FIBK

When we refer to “we,” “our,” “us,” “First Interstate,” or the “Company” in this report, we mean First Interstate BancSystem, Inc. and our consolidated subsidiaries, including our wholly owned subsidiary, First Interstate Bank, unless the context indicates that we refer only to the parent company, First Interstate BancSystem, Inc. When we refer to the “Bank” or “FIB” in this report, we mean only First Interstate Bank. The following discussion of our consolidated financial data reflects our historical results of operations and financial condition and should be read in conjunction with our financial statements and accompanying notes presented elsewhere in this Quarterly Report on Form 10-Q and in our Annual Report on Form 10-K for the year ended December 31, 2025, including the audited financial statements and related notes contained therein, as previously filed with the Securities and Exchange Commission, or SEC. Cautionary Note Regarding Forward-Looking Statements and Factors that Could Affect Future Results This Quarterly Report on Form 10-Q contains forward-looking statements within the meaning of Section 27A of the Securities Act of 1933, as amended, and Rule 175 promulgated thereunder, and Section 21E of the Securities Exchange Act of 1934, as amended, or the Exchange Act, and Rule 3b-6 promulgated thereunder, that involve inherent risks and uncertainties. Any statements about our plans, objectives, expectations, strategies, beliefs, or future performance, financial condition, results of operations, investment portfolio, market position, or events constitute forward-looking statements. Such statements are identified by words or phrases such as “believes,” “expects,” “anticipates,” “plans,” “trends,” “objectives,” “views,” “continues,” “projected,” as well as the negative forms of those words or similar expressions, or future or conditional verbs such as “will,” “would,” “should,” “could,” “seek,” “might,” “may,” as well as the negative forms of those words or similar expressions. Forward-looking statements involve known and unknown risks, uncertainties, assumptions, estimates and other important factors that could cause actual results to differ materially from any results, performance or events expressed or implied by such forward-looking statements. A detailed discussion of risks that may cause actual results to differ materially from current expectations in the forward-looking statements is included below in this report under the caption “Risk Factors” and in our Annual Report on Form 10-K for the year ended December 31, 2025, under the captions “Cautionary Note Regarding Forward-Looking Statements” and “Risk Factors”. These factors and the other risk factors described in our periodic and current reports filed with the SEC from time to time, however, are not necessarily all of the important factors that could cause our actual results, performance, or achievements to differ materially from those expressed in or implied by any of our forward-looking statements. Other unknown or unpredictable factors also could harm our results. All forward-looking statements attributable to us or persons acting on our behalf are expressly qualified in their entirety by the cautionary statements set forth above. Interested parties are urged to read in their entirety the referenced risk factors prior to making any investment decision with respect to the Company. Forward-looking statements speak only as of the date they are made, and we do not undertake or assume any obligation to update publicly any of these statements to reflect actual results, new information or future events, changes in assumptions or changes in other factors affecting forward-looking statements, except to the extent required by applicable laws. If we update one or more forward-looking statements, no inference should be drawn that we will make additional updates with respect to those or other forward-looking statements. Non-GAAP Financial Measures In addition to financial measures presented in accordance with generally accepted accounting principles (“GAAP”) in the United States, this document contains non-GAAP financial measures where management believes it would be helpful to understand our results of operations or financial position. The Company’s management believes that the non-GAAP financial measures provide additional intelligence about ongoing operations and enhance comparability of results of operations with prior periods by presenting financial results without the impact of items or events that may obscure trends in the Company’s underlying performance. This information should be considered as supplemental in nature and should not be considered in isolation or as a substitute for the related financial information prepared in accordance with GAAP. Where non-GAAP financial measures are used, the comparable GAAP financial measure, as well as the reconciliation to the comparable GAAP financial measure, can be found herein. 39 Table of Contents Fully-Taxable Equivalent Basis. The Company adjusts its net interest income to include its interest income on a fully-taxable equivalent (FTE) basis and further adjusts to exclude purchase accounting interest accretion on acquired loans. Interest income, yields, and ratios on an FTE basis are considered non-GAAP financial measures. Net interest margin (FTE) is calculated as annualized net interest income on an FTE basis divided by average earning assets. Management believes net interest income on an FTE basis provides an insightful picture of the interest margin for comparison purposes. The FTE basis also allows management to assess the comparability of revenue arising from both taxable and tax-exempt sources. The FTE basis assumes a federal statutory tax rate of 21 percent. These measures are considered standard measures of comparison within the banking industry. We encourage readers to consider the Unaudited Consolidated Financial Statements and other financial information contained in this Form 10-Q in their entirety, and not to rely on any single financial measure. See “Non-GAAP Reconciliations” included herein for a reconciliation to the most directly comparable GAAP financial measures. Limitations associated with non-GAAP financial measures include the risks that persons might disagree as to the appropriateness of items included in these measures and that other companies might calculate these measures differently. These non-GAAP disclosures should not be considered an alternative to the Company’s GAAP results. Executive Overview We are a financial and bank holding company focused on community banking. Since our incorporation in Montana in 1971, we have grown both organically and through strategic acquisitions. As of July 30, 2026, we operated 271 banking offices, including branches and detached drive-up facilities, in communities across ten states—Colorado, Idaho, Iowa, Missouri, Montana, Nebraska, Oregon, South Dakota, Washington, and Wyoming. Through our bank subsidiary, First Interstate Bank, we deliver a comprehensive range of banking products and services—including online and mobile banking—to individuals, businesses, government entities, and others throughout our market areas. We are proud to provide financial services and products to clients that participate in a wide variety of industries, including: •Agriculture •Healthcare •Professional services •Technology •Construction •Hospitality •Real Estate Development •Tourism •Education •Housing •Retail •Wholesale trade •Governmental services As of June 30, 2026, we had consolidated assets of $25.9 billion, deposits of $21.4 billion, net loans held for investment of $14.1 billion, and total stockholders’ equity of $3.3 billion. Our strategy emphasizes disciplined, relationship-driven organic growth by deepening and expanding client relationships across deposits, lending and fee-based services. We continue to execute our strategic plan to refocus capital investment, optimize our balance sheet and improve core profitability, including by prioritizing investment in core markets where we have brand density and attractive growth prospects, optimizing our branch network, emphasizing relationship-based business and disciplined underwriting, and aligning our organization to support timely local decision-making. Our Business Our principal business activity is lending to, accepting deposits from, and conducting financial transactions for individuals, businesses, governmental entities, and other entities located in the communities we serve. We derive our income principally from interest charged on loans and, to a lesser extent, from interest and dividends earned on fixed income investments. We also derive income from noninterest sources such as: (i) fees received in connection with various lending and deposit services; (ii) wealth management services, such as trust, employee benefit, investment, and insurance services; (iii) mortgage loan originations, sales, and servicing; (iv) merchant and electronic banking services; and (v) from time-to-time, gains on sales of assets and securities. Our principal expenses include: (i) interest expense on deposit accounts and other borrowings; (ii) salaries and employee benefits; (iii) information technology and communication costs primarily associated with maintaining loan and deposit functions; (iv) furniture, equipment, and occupancy expenses for maintaining our facilities; (v) professional fees, including Federal Deposit Insurance Corporation (“FDIC”) insurance assessments; (vi) income tax expense; (vii) provisions for credit losses; (viii) intangible amortization; (ix) other real estate owned expenses; and (x) other segment expenses including advertising and promotion, donations, credit card rewards expense, fees associated with originating and closing loans, insurance, and other expenses necessary to support our employees and service our clients. From time to time, we have incurred, and may incur in the future, costs related to our strategic acquisitions, divestitures and other transactions. 40 Table of Contents Our loan portfolio consists of a mix of real estate, consumer, commercial, agricultural, and other loans, including fixed, adjustable, and variable rate loans. Our real estate loans comprise commercial real estate, construction (including residential, commercial, and land development construction loans), residential, agricultural, and other real estate loans. Fluctuations in the loan portfolio are directly related to the economies of the communities we serve. While each loan we originate must meet minimum underwriting standards we establish through our credit policies, our bankers are granted limited discretion to approve and price loans within pre-approved limits which assures that we are responsive to community needs in each market area and remain competitive. We fund our loan portfolio primarily with the core deposits from our clients. Historically, we have not relied on brokered deposits as a source of funding. We have also utilized wholesale funding sources to a limited extent. Recent Trends and Developments Our community banking footprint spans across the Rocky Mountain, Pacific Northwest, and Midwest regions. Stock Repurchase Program On August 28, 2025, the board of directors of the Company adopted a new stock repurchase program, pursuant to which the Company has been authorized to repurchase up to $150.0 million of its issued and outstanding shares of common stock on or prior to March 31, 2027, which is the expiration date of the program. On January 27, 2026, the board of directors authorized an increase to the repurchase program of an additional $150.0 million and on July 22, 2026, the board of directors authorized an additional increase to the repurchase program of an additional $150.0 million, or a total of $450.0 million authorized since its adoption in August of 2025. Any repurchased shares will be returned to authorized but unissued shares of common stock, as permitted under applicable Delaware law. As of July 30, 2026, approximately $170.4 million remained available for future purchases under the $450.0 million authorized. Sale of Certain Nebraska Branches On April 10, 2026, the Bank closed the previously disclosed transaction with Security First Bank (“Security First”) for a gain of $19.5 million, pursuant to which Security First acquired eleven Nebraska branches from the Bank, including approximately $244.2 million in deposits and loans with outstanding balances of $64.1 million and the owned real estate and fixed and other assets associated with the branches. Closure of Four Nebraska Branches The Company closed four additional branches in Nebraska in the first quarter of 2026. These branch closures were intended to enhance operational efficiency and better position the Company for long-term success. Subsequent to the sale and closures, the Company has 29 branches remaining in Nebraska. Closure and Exit of North Dakota and Minnesota Branches; Branch Opening in Montana The Company exited the States of North Dakota and Minnesota during the first quarter of 2026, by closing the single branch location in each of those states. One branch in Billings, Montana opened in February 2026. Closure of Iowa Branch and Oregon Branch, and Pending Closure of Washington Branch As previously announced, following a strategic review, the Company closed two branches, one branch in Iowa and one branch in Oregon on July 10, 2026 and intends to close one branch in Washington during the third quarter of 2026. These branch closures are intended to enhance operational efficiency and better position the Company for long-term success. Banking Organization Redesign During the first quarter of 2026, the Company completed the previously announced transformation of its banking organization from a layered regional and market structure to a flatter model designed to enable decisions to be made closer to the client. The redesign included the appointment of new State Presidents at the Bank, a majority of whom were from within the Bank and supplemented by select external hires, and a more streamlined chain of responsibility intended to speed up local decision-making, support improved accountability, and align decision-making with the Company’s relationship-driven organic growth strategy. Indirect Loans In January 2025, we announced our plans to stop originating indirect loans as of February 28, 2025. Under our indirect lending program, indirect loans were created when we purchased consumer loan contracts advanced for the purchase of automobiles, boats, recreational vehicles, and other consumer goods from the consumer product dealer network within the market areas we serve. Since discontinuing new originations, the indirect loan portfolio has continued to decline through scheduled amortization and normal portfolio runoff. This runoff is expected to continue over the remaining contractual terms of the existing loans, which generally mature in seven years or less. At June 30, 2026, the Company’s $369.0 million of indirect loans represented approximately 2.6% of loan balances and 74.7% of our consumer loan portfolio. 41 Table of Contents Economic Conditions The Company has ample liquidity, and its capital ratios exceed all regulatory requirements to be deemed “well-capitalized” as of June 30, 2026. Our deposit base is diversified, including by depositor, which includes individuals, businesses across multiple industries, governmental units, and other entities, as well as geographically, across the communities we serve in our 10-state footprint. As of June 30, 2026, our FDIC insured deposits were 63.1% of total deposits, including accounts eligible for pass-through insurance. As of July 30, 2026, the Bank had available borrowing capacity of $4.8 billion with the Federal Home Loan Bank (“FHLB”) and $5.0 billion with the Federal Reserve Bank (“FRB”) based on pledged investment securities and loan collateral. The Company’s quarterly yield on interest earning assets increased to 4.65% for the three months ended June 30, 2026 from 4.63% for the three months ended March 31, 2026, and decreased from 4.76% for the three months ended June 30, 2025. Lower short-term interest rates have benefited the Company’s cost of funds, primarily resulting in reduced rates on variable rate debt and deposits. The Company’s cost of funds decreased to 1.23% during the three months ended June 30, 2026 from 1.27% during the three months ended March 31, 2026. During the second quarter of 2026, the changes in the mix and cost of funds were partially supported by the changes in the mix and yield on earning assets, resulting in an increase in the Company’s net interest margin to 3.45% during the three months ended June 30, 2026, from 3.41% during the three months ended March 31, 2026. The Company’s net FTE interest margin, a non-GAAP financial measure, increased to 3.48% during the three months ended June 30, 2026, from 3.43% during the three months ended March 31, 2026. The Company expects to see continued volatility in the economic markets, which may include recessionary signs in the economy resulting from, among other things, uncertain conditions due to changes in U.S. policies like the implementation of new tariffs, retaliatory tariffs, and other trade policies as well as geopolitical uncertainty, including the recent military conflict involving Iran and related disruptions in global energy markets. These uncertain conditions could have adverse impacts on the balance sheet and income statement of the Company for the remainder of the year. A slowdown, downturn, or recession in the U.S. economy or changes in U.S. trade policies could impact the Company, including by impacting the level of deposits held by our clients, whether through a higher volume of withdrawals or through a lower volume of deposits. Client deposits are one of the Company’s primary lending sources. The credit quality of the Company’s loans may also be impacted if clients must weather adverse economic conditions which could result in an increase in credit losses or other related expenses. For example, the estimated effects of current and forecasted economic conditions are reflected in the Company’s provision for credit losses and allowance for credit losses. During the second quarter of 2026, the Company recorded a $3.2 million reversal of provision for credit losses, and the allowance for credit losses decreased to 1.28% of loans held for investment at June 30, 2026, from 1.33% at March 31, 2026. During the same period, non-performing assets increased approximately 1.5% while criticized loans decreased 9.3%. For additional information regarding non-performing assets, allowance for credit losses, and credit quality indicators, see “Note – Loans Held for Investment – Credit Quality Indicators” in the accompanying “Notes to Unaudited Consolidated Financial Statements” included in this report. Primary Factors Used in Evaluating Our Business As a banking institution, we manage and evaluate our financial condition and our results of operations. We monitor and evaluate the levels and trends of the line items included in our balance sheet and statements of income, as well as the various financial ratios that are commonly used in our industry. We analyze these ratios and financial trends against both our own historical levels as well as the financial condition and performance of comparable banking institutions in our region and nationally. As discussed in our Annual Report on Form 10-K for the year ended December 31, 2025, our financial performance is impacted by a number of external factors outside our control, as well as our ability to execute on the key components of our strategy for continued success and future growth. See Part II – Other Information, “Item 1A – Risk Factors” herein for additional information regarding risk factors that may negatively impact our expected results, performance, or achievements. 42 Table of Contents Critical Accounting Estimates and Significant Accounting Policies Our consolidated financial statements are prepared in accordance with GAAP and follow general practices within the banking industry. Application of these principles requires management to make estimates, assumptions, and judgments that affect the amounts reported in the consolidated financial statements and accompanying notes. The most significant accounting policies we follow are summarized in Note 1 of the Notes to Consolidated Financial Statements included in our Annual Report on Form 10-K for the year ended December 31, 2025, and are also referenced in “Note 1 – Basis of Presentation” in the accompanying “Notes to Unaudited Consolidated Financial Statements” included in this report. There have been no material changes during the second quarter of 2026 in our critical accounting estimates and policies from the critical accounting estimates and policies as described in our Annual Report on Form 10-K for the year ended December 31, 2025. The preparation of financial statements in conformity with GAAP requires management to measure the Company’s financial position and operating results primarily in terms of historic dollars. Changes in the relative value of money due to inflation or recession are generally not considered. We manage our interest rate risk in several ways. Refer to “Note – Derivatives and Hedging Activities” in the accompanying “Notes to Unaudited Consolidated Financial Statements” included in this report for further discussion on how we manage interest rate risk. There can be no assurance that we will not be materially adversely affected by future changes in interest rates, as interest rates are highly sensitive to many factors that are beyond our control. Results of Operations The following discussion and analysis is intended to provide detail about the results of our operations and financial condition. More information regarding the results as of December 31, 2025 can be found in our Annual Report on Form 10-K for the year ended December 31, 2025. Net Income Net income increased $12.2 million to $83.9 million, or $0.87 per diluted share, during the three months ended June 30, 2026, as compared to net income of $71.7 million, or $0.69 per diluted share, for the same period in 2025, which is primarily attributable to the $19.5 million gain recorded from the previously announced sale of the eleven Nebraska branches during the second quarter of 2026, partially offset by lower net interest income. Net income increased $22.2 million to $144.1 million, or $1.47 per diluted share, during the six months ended June 30, 2026, as compared to net income of $121.9 million, or $1.18 per diluted share, for the same period in 2025, which is primarily attributable to the $19.5 million gain recorded from the previously announced sale of the eleven Nebraska branches during the second quarter of 2026, partially offset by lower net interest income for the 2026 period. Net Interest Income Net interest income, the largest source of our operating income, is derived from interest, dividends, and fees received on interest earning assets, less interest expense incurred on interest bearing liabilities. Interest earning assets primarily include loans and investment securities. Interest bearing liabilities include deposits, short-term borrowings, and various other forms of indebtedness. Net interest income is affected by the level of interest rates, changes in interest rates, the speed of changes to interest rates, and changes in the volume and composition of interest earning assets and interest bearing liabilities. Changes in the interest rate spread, which is the difference between interest earned on assets and interest paid on liabilities, has the most significant impact on net interest income. Other factors like volume of loans, investment securities, and other interest earning assets compared to the volume of interest bearing deposits, short-term borrowings, and other indebtedness also cause changes in our net interest income between periods. Noninterest bearing sources of funds, such as demand deposits and stockholders’ equity, help to support earning assets. For the periods indicated, the following table presents average balance sheet information, together with interest income and yields earned on average interest earning assets and interest expense and rates paid on average interest bearing liabilities. 43 Table of Contents Average Balance Sheets, Yields and Rates Three Months Ended (Dollars in millions) June 30, 2026 June 30, 2025 Average Balance Interest(3) (6) Average Rate Average Balance Interest(3) (6) Average Rate Interest earning assets: Loans (1) $ 14,524.6 $ 203.5 5.62 % $ 17,053.8 $ 240.2 5.65 % Investment securities: Taxable (2) 7,873.5 58.8 3.00 7,254.3 49.6 2.74 Tax-exempt 175.1 0.9 2.06 181.7 0.8 1.77 Investment in FHLB and FRB stock 106.5 1.3 4.90 139.3 2.1 6.05 Interest bearing deposits in banks 805.1 7.5 3.74 550.9 6.2 4.51 Federal funds sold 0.1 — — 0.1 — — Total interest earning assets $ 23,484.9 $ 272.0 4.65 % $ 25,180.1 $ 298.9 4.76 % Noninterest earning assets 2,622.5 2,718.3 Total assets $ 26,107.4 $ 27,898.4 Interest bearing liabilities: Demand deposits $ 6,252.5 $ 14.0 0.90 % $ 6,402.9 $ 15.0 0.94 % Savings deposits 7,789.8 32.9 1.69 7,801.3 36.6 1.88 Time deposits 2,302.4 15.6 2.72 2,806.2 23.7 3.39 Repurchase agreements 460.1 0.9 0.78 517.4 1.1 0.85 Other borrowed funds 4.0 — — 720.4 8.3 4.62 Long-term debt 146.8 2.6 7.10 158.4 2.7 6.84 Subordinated debentures held by subsidiary trusts 149.9 2.4 6.42 163.1 2.9 7.13 Total interest bearing liabilities $ 17,105.5 $ 68.4 1.60 % $ 18,569.7 $ 90.3 1.95 % Noninterest bearing deposits 5,290.5 5,561.3 Other noninterest bearing liabilities 353.7 366.3 Stockholders’ equity 3,357.7 3,401.1 Total liabilities and stockholders’ equity $ 26,107.4 $ 27,898.4 Net FTE interest income (non-GAAP)(4) $ 203.6 $ 208.6 Less FTE adjustments(3) (1.4) (1.4) Net interest income from consolidated statements of income $ 202.2 $ 207.2 Interest rate spread 3.05 % 2.81 % Net interest margin 3.45 3.30 Net FTE interest margin (non-GAAP)(4) 3.48 3.32 Cost of funds, including noninterest bearing demand deposits (5) 1.23 1.50 (1) Average loan balances include loans held for sale and loans held for investment, net of deferred fees and costs, which include non-accrual loans. Interest income includes amortization of deferred loan fees net of deferred loan costs, which is not material. (2) Includes average balance of unsettled trades on investment securities. (3) The Company adjusts interest income and average rates for tax-exempt loans and securities to an FTE basis utilizing a 21% tax rate. (4) Management believes fully taxable equivalent, or FTE, interest income is useful to investors in evaluating the Company’s performance as a comparison of the returns between a tax-free investment and a taxable alternative. Net FTE interest income and net FTE interest margin are non-GAAP financial measures. See “Non-GAAP Reconciliations” included herein for a reconciliation to the most directly comparable GAAP financial measures. (5) Calculated by dividing total annualized interest on interest bearing liabilities by the sum of total interest bearing liabilities plus noninterest bearing deposits. (6) Dividends on FHLB and FRB stock. Net interest income decreased $5.0 million during the three months ended June 30, 2026, as compared to the same period in 2025. The decrease was partially influenced by the reduction in loans and deposits related to the sale of the Arizona and Kansas branches during the fourth quarter of 2025 and sale of eleven Nebraska branches during the second quarter of 2026, which resulted in a reduction of net interest income in the second quarter of 2026. Net interest income included interest accretion related to the fair value of acquired loans of $3.5 million during the three months ended June 30, 2026, compared to interest accretion of $4.2 million during the three months ended June 30, 2025. 44 Table of Contents Our net interest margin ratio increased 15 basis points to 3.45% for the three months ended June 30, 2026, as compared to 3.30% for the same period in 2025 and our net FTE interest margin ratio, a non-GAAP financial measure, increased 16 basis points for the three months ended June 30, 2026, as compared to the same period in 2025. Exclusive of the impact of interest accretion on acquired loans, the net FTE interest margin ratio increased 16 basis points to 3.42% during the three months ended June 30, 2026, as compared to 3.26% for the same period in 2025. The increases in the net interest margin ratio were primarily a result of lower interest expense resulting from decreased other borrowed funds balances. Average Balance Sheets, Yields and Rates Six Months Ended (Dollars in millions) June 30, 2026 June 30, 2025 Average Balance Interest(3) (6) Average Rate Average Balance Interest(3) (6) Average Rate Interest earning assets: Loans (1) $ 14,776.8 $ 411.1 5.61 % $ 17,359.4 $ 483.7 5.62 % Investment securities Taxable (2) 7,789.8 114.0 2.95 7,358.7 100.9 2.77 Tax-exempt 175.6 1.7 1.95 182.2 1.7 1.88 Investment in FHLB and FRB stock 106.4 2.5 4.74 157.5 5.0 6.40 Interest bearing deposits in banks 826.8 15.3 3.73 559.2 12.5 4.51 Federal funds sold 0.1 — — 0.1 — — Total interest earning assets $ 23,675.5 $ 544.6 4.64 % $ 25,617.1 $ 603.8 4.75 % Noninterest earning assets 2,617.9 2,739.0 Total assets $ 26,293.4 $ 28,356.1 Interest bearing liabilities: Demand deposits $ 6,226.4 $ 26.8 0.87 % $ 6,407.8 $ 29.4 0.93 % Savings deposits 7,833.1 65.6 1.69 7,800.8 72.3 1.87 Time deposits 2,428.7 34.7 2.88 2,834.4 48.7 3.46 Repurchase agreements 469.8 1.9 0.82 525.2 2.3 0.88 Other borrowed funds 2.0 — — 1,124.7 25.8 4.63 Long-term debt 146.6 5.2 7.15 145.3 4.4 6.11 Subordinated debentures held by subsidiary trusts 149.9 4.8 6.46 163.1 5.7 7.05 Total interest bearing liabilities $ 17,256.5 $ 139.0 1.62 % $ 19,001.3 $ 188.6 2.00 % Noninterest bearing deposits 5,252.5 5,584.6 Other noninterest bearing liabilities 382.3 392.0 Stockholders’ equity 3,402.1 3,378.2 Total liabilities and stockholders’ equity $ 26,293.4 $ 28,356.1 Net FTE interest income (non-GAAP)(3) $ 405.6 $ 415.2 Less FTE adjustments (3) (2.7) (3.0) Net interest income from consolidated statements of income $ 402.9 $ 412.2 Interest rate spread 3.02 % 2.75 % Net interest margin 3.43 3.24 Net FTE interest margin (non-GAAP)(4) 3.45 3.27 Cost of funds, including noninterest bearing demand deposits (5) 1.25 1.55 (1) Average loan balances include loans held for sale and loans held for investment, net of deferred fees and costs, which include non-accrual loans. Interest income includes amortization of deferred loan fees net of deferred loan costs, which is not material. (2) Includes average balance of unsettled trades on investment securities. (3) The Company adjusts interest income and average rates for tax-exempt loans and securities to an FTE basis utilizing a 21% tax rate. (4) Management believes fully taxable equivalent, or FTE, interest income is useful to investors in evaluating the Company’s performance as a comparison of the returns between a tax-free investment and a taxable alternative. Net FTE interest income and net FTE interest margin are non-GAAP financial measures. See “Non-GAAP Reconciliations” included herein for a reconciliation to the most directly comparable GAAP financial measures. (5) Calculated by dividing total annualized interest on interest bearing liabilities by the sum of total interest bearing liabilities plus non-interest bearing deposits. (6) Dividends on FHLB and FRB stock. 45 Table of Contents Net interest income decreased $9.3 million during the six months ended June 30, 2026, as compared to the same period in 2025, primarily due to lower interest income on loans as a result of a decrease in average rates and average loan balances driven by the sale of the Arizona and Kansas branches during the fourth quarter of 2025 and the sale of eleven Nebraska branches during the second quarter of 2026, partially offset by a decrease in interest expense resulting from decreased rates on other borrowed funds and deposits along with a decrease in average other borrowed funds balances and higher interest income on investment securities as a result of an increase in average rates and average investment security balances. Net interest income included interest accretion related to the fair value of acquired loans of $6.6 million during the six months ended June 30, 2026, compared to interest accretion of $8.9 million during the six months ended June 30, 2025. Our net interest margin ratio increased 19 basis points to 3.43% for the six months ended June 30, 2026, as compared to 3.24% for the same period in 2025 and our net FTE interest margin ratio, a non-GAAP financial measure, increased 18 basis points for the six months ended June 30, 2026, as compared to the same period in 2025. Exclusive of the impact of interest accretion on acquired loans, the net FTE interest margin ratio increased 20 basis points to 3.40% during the six months ended June 30, 2026, as compared to 3.20% for the same period in 2025. The increases in the net interest margin ratio were primarily a result of lower interest expense resulting from decreased other borrowed funds balances. The table below sets forth a summary of the changes in interest income and interest expense resulting from estimated changes in average asset and liability balances (volume) and estimated changes in average interest rates (referred to as “rate”) for the three and the six months ended June 30, 2026 and 2025. Changes which are not due solely to volume or rate have been allocated to these categories based on the respective percent changes in average volume and average rate as they compare to each other. Analysis of Interest Changes Due to Volume and Rates (Dollars in millions) Three Months Ended June 30, 2026 compared with Three Months Ended June 30, 2025 Six Months Ended June 30, 2026 compared with Six Months Ended June 30, 2025 Volume Rate(2) Net Volume Rate(2) Net Interest earning assets: Loans (1) $ (35.6) $ (1.1) $ (36.7) $ (72.0) $ (0.6) $ (72.6) Investment securities (1) 4.2 5.1 9.3 5.8 7.3 13.1 Investment in FHLB and FRB stock (0.5) (0.3) (0.8) (1.6) (0.9) (2.5) Interest bearing deposits in banks 2.9 (1.6) 1.3 6.0 (3.2) 2.8 Total change (29.0) 2.1 (26.9) (61.8) 2.6 (59.2) Interest bearing liabilities: Demand deposits (0.4) (0.6) (1.0) (0.8) (1.8) (2.6) Savings deposits (0.1) (3.6) (3.7) 0.3 (7.0) (6.7) Time deposits (4.3) (3.8) (8.1) (7.0) (7.0) (14.0) Repurchase agreements (0.1) (0.1) (0.2) (0.2) (0.2) (0.4) Other borrowed funds (8.3) — (8.3) (25.8) — (25.8) Long-term debt (0.2) 0.1 (0.1) — 0.8 0.8 Subordinated debentures held by subsidiary trusts (0.2) (0.3) (0.5) (0.5) (0.4) (0.9) Total change (13.6) (8.3) (21.9) (34.0) (15.6) (49.6) Increase in net FTE interest income (1) $ (15.4) $ 10.4 $ (5.0) $ (27.8) $ 18.2 $ (9.6) (1)Interest income and average rates for tax-exempt loans and securities are presented on a FTE basis. (2)Dividends on FHLB and FRB stock are used to determine the rate. 46 Table of Contents Non-GAAP Reconciliations The table below provides a reconciliation of the non-GAAP financial measures to the most directly comparable GAAP financial measure. Three Months Ended Six Months Ended (In millions, except % and per share data) June 30, 2026 March 31, 2026 June 30, 2025 Jun 30, 2026 Jun 30, 2025 Net interest income (A) $ 202.2 $ 200.7 $ 207.2 $ 402.9 $ 412.2 FTE interest income 1.4 1.3 1.4 2.7 3.0 Net FTE interest income (Non-GAAP) (B) 203.6 202.0 208.6 405.6 415.2 Less purchase accounting accretion on acquired loans 3.5 3.1 4.2 6.6 8.9 Adjusted net FTE interest income (Non-GAAP) (C) $ 200.1 $ 198.9 $ 204.4 $ 399.0 $ 406.3 Average interest earning assets (D) $ 23,484.9 $ 23,868.3 $ 25,180.1 $ 23,675.5 $ 25,617.1 Net interest margin (GAAP) (A*) / (D) 3.45 % 3.41 % 3.30 % 3.43 % 3.24 % Net FTE interest margin ratio (Non-GAAP) (B*) / (D) 3.48 3.43 3.32 3.45 3.27 Adjusted net FTE interest margin ratio (Non-GAAP) (C*) / (D) 3.42 3.38 3.26 3.40 3.20 *Annualized Provision for Credit Losses Fluctuations in the provision for credit losses reflect charge-offs and recoveries as well as management’s estimate of possible credit losses based upon the composition of our loan portfolio, evaluation of the borrowers’ ability to repay, collateral value of underlying loans, loan loss trends, and estimated effects of current and forecasted economic conditions on our loans held for investment and investment securities portfolios. The Company recorded a $3.2 million reduction of credit losses, resulting from a reduction of credit losses of $3.9 million on loans held for investment, a provision for credit losses for unfunded commitments of $1.1 million, and a reduction of credit losses on investment securities of $0.4 million during the three months ended June 30, 2026, as compared to a $0.3 million reduction of credit losses during the same period in 2025. Net charge-offs were $9.7 million or an annualized 0.27% of average loans outstanding during the three months ended June 30, 2026, as compared to net charge-offs of $5.8 million, or an annualized 0.14% of average loans outstanding during the same period in 2025. Net loan charge-offs in the second quarter of 2026 were composed of charge-offs of $14.0 million, which were partially offset by recoveries of $4.3 million. The provision for credit losses during the six months ended June 30, 2026 of $3.5 million included a provision for credit losses on loans held for investment of $2.9 million, a provision for credit losses on unfunded commitments of $1.0 million, and a reduction of credit losses on investment securities of $0.4 million. This compares to a provision for credit losses of $19.7 million during the same period in 2025. Net charge-offs were $12.1 million or an annualized 0.17% of average loans outstanding during the six months ended June 30, 2026, as compared to net charge-offs of $14.8 million, or an annualized 0.17% of average loans outstanding during the same period in 2025. Net loan charge-offs during the six months ended June 30, 2026 were composed of charge-offs of $20.5 million, which were partially offset by recoveries of $8.4 million. For information regarding our non-performing loans, see “Financial Condition – Non-Performing Assets” included herein. For more information on our allowance for credit losses, see “Financial Condition – Allowance for Credit Losses” included herein. 47 Table of Contents Noninterest Income Noninterest income also contributes to our operating results with fee-based revenues such as payment services, mortgage banking and wealth management revenues, service charges on deposit accounts, and other service charges, commissions and fees. The following table presents the composition of our noninterest income for the periods indicated: Noninterest Income Three Months Ended June 30, $ Change % Change Six Months Ended June 30, $ Change % Change (Dollars in millions) 2026 2025 2026 2025 Payment services revenues $ 16.8 $ 17.8 $ (1.0) (5.6) % $ 32.4 $ 34.9 $ (2.5) (7.2) % Mortgage banking revenues 1.5 1.8 (0.3) (16.7) 2.8 3.2 (0.4) (12.5) Wealth management revenues 10.6 9.7 0.9 9.3 21.1 19.5 1.6 8.2 Service charges on deposit accounts 6.6 6.9 (0.3) (4.3) 13.1 13.5 (0.4) (3.0) Other service charges, commissions and fees 1.9 2.1 (0.2) (9.5) 4.0 4.4 (0.4) (9.1) Other income 4.8 2.8 2.0 71.4 9.9 7.6 2.3 30.3 Gain on sale of branches, net 19.5 — 19.5 100.0 19.5 — 19.5 100.0 Total noninterest income $ 61.7 $ 41.1 $ 20.6 50.1 $ 102.8 $ 83.1 $ 19.7 23.7 Noninterest income increased $20.6 million during the three months ended June 30, 2026 compared to the same period in 2025 primarily driven by an increase of $19.5 million related to the gain recorded on the previously announced sale of the eleven Nebraska branches during the second quarter of 2026. For the six months ended June 30, 2026, noninterest income increased $19.7 million, as compared to the same period in 2025 driven by an increase of $19.5 million related to the gain recorded on the previously announced sale of the eleven Nebraska branches during the second quarter of 2026 and an increase in wealth management revenues mainly as a result of increased trust and estate fees, partially offset by a decrease in payment services revenues which was mainly the result of outsourcing the consumer credit card portfolio in the second quarter of 2025. Noninterest Expense The following table presents the composition of our noninterest expense for the periods indicated: Noninterest Expense Three Months Ended June 30, $ Change % Change Six Months Ended June 30, $ Change % Change (Dollars in millions) 2026 2025 2026 2025 Salaries and wages $ 64.9 $ 65.0 $ (0.1) (0.2) % $ 133.4 $ 133.6 $ (0.2) (0.1) % Employee benefits 19.0 17.9 1.1 6.1 40.2 37.9 2.3 6.1 Outsourced technology services 16.7 13.3 3.4 25.6 32.6 27.5 5.1 18.5 Occupancy, net 13.6 13.4 0.2 1.5 27.0 27.1 (0.1) (0.4) Furniture and equipment 4.4 5.2 (0.8) (15.4) 9.6 10.2 (0.6) (5.9) OREO expense, net of income 0.6 — 0.6 — (0.5) 0.5 (1.0) (200.0) Professional fees 6.1 5.7 0.4 7.0 11.0 11.2 (0.2) (1.8) FDIC insurance premiums 3.4 4.0 (0.6) (15.0) 6.2 8.3 (2.1) (25.3) Other intangibles amortization 3.3 3.4 (0.1) (2.9) 6.6 6.8 (0.2) (2.9) Other expenses 26.9 27.2 (0.3) (1.1) 50.4 52.6 (2.2) (4.2) Total noninterest expense $ 158.9 $ 155.1 $ 3.8 2.5 $ 316.5 $ 315.7 $ 0.8 0.3 Noninterest expense increased $3.8 million during the three months ended June 30, 2026 compared to the same period in 2025, and increased $0.8 million during the six months ended June 30, 2026. Employee benefits expense increased $1.1 million during the three months ended June 30, 2026 as compared to the same period in 2025, primarily due to higher health insurance costs of $1.0 million during the second quarter of 2026. Employee benefits expense increased $2.3 million during the six months ended June 30, 2026 as compared to the same period in 2025, primarily due to higher health insurance costs of $4.1 million, partially offset by lower long-term incentives of $1.4 million during the 2026 period. 48 Table of Contents Outsourced technology services increased $3.4 million during the three months ended June 30, 2026 as compared to the same period in 2025, and increased $5.1 million during the six months ended June 30, 2026 primarily due to increases in account processing software costs and an increase in software service costs. Other Real Estate Owned (“OREO”) expense, net increased $0.6 million during the three months ended June 30, 2026 as compared to the same period in 2025, and decreased $1.0 million during the six months ended June 30, 2026, as compared to the same period in 2025. The decrease during the six months ended June 30, 2026 was primarily due to a positive fair value adjustment to a commercial property during the first quarter of 2026. FDIC insurance premiums decreased $0.6 million during the three months ended June 30, 2026 as compared to the same period in 2025, and decreased $2.1 million during the six months ended June 30, 2026, primarily attributable to lower FDIC assessment rates in 2026 due to lower average assets and as a result of an adjustment to the special assessment accrual to cover the losses incurred by the Deposit Insurance Fund (“DIF”) in response to the 2023 bank failures. Other expenses primarily include advertising and public relations costs; office supply, postage, freight, telephone, and travel expenses; donations expense; debit and credit card expenses; board of director fees; legal expenses; and other losses. Other expenses decreased $0.3 million during the three months ended June 30, 2026 compared to the same period in 2025, and decreased $2.2 million during the six months ended June 30, 2026, primarily resulting from decreases in donation expense and losses on sale of fixed assets. Income Tax Expense Our effective federal tax rate was 17.4% for the three months ended June 30, 2026 compared to 18.4% for the three months ended June 30, 2025, and was 17.6% for the six months ended June 30, 2026 compared to 18.6% for the same period in 2025. Fluctuations in effective federal income tax rates are primarily driven by changes in actual and forecasted pre-tax income. State income tax applies primarily to pretax earnings generated within Colorado, Idaho, Iowa, Missouri, Montana, Oregon, and South Dakota. Our effective state tax rate was 5.1% for the three months ended June 30, 2026 compared to 4.9% for the three months ended June 30, 2025 and was 4.8% and 5.2% for the six months ended June 30, 2026 and 2025, respectively. Financial Condition Total Assets Total assets decreased $755.6 million, or 2.8%, to $25,885.0 million as of June 30, 2026, from $26,640.6 million as of December 31, 2025, primarily due to decreases in loans and cash and cash equivalents which were partially offset by an increase in investment securities. Significant fluctuations in balance sheet accounts are discussed below. More information regarding the results as of December 31, 2025 can be found in our Annual Report on Form 10-K for the year ended December 31, 2025. Investment Securities We manage our investment portfolio to obtain the highest yield possible while meeting our credit and interest rate risk tolerance and liquidity guidelines and satisfying the pledging requirements for deposits of state and political subdivisions and securities sold under repurchase agreements. Our portfolio principally comprises U.S. treasury notes, obligations of U.S. government agencies, U.S. government agency commercial mortgage-backed securities, U.S. agency government residential mortgage-backed securities, U.S. government agency collateralized mortgage obligations, collateralized loan obligation, corporate securities, and tax-exempt municipal securities. Debt securities rated in the highest category by nationally recognized rating agencies and debt securities backed by the U.S. Government and government sponsored agencies, both on a direct and indirect basis, represented approximately 96.4% and 95.1% of the investment portfolio’s available-for-sale and held-to-maturity segments, respectively, at June 30, 2026. Investment securities increased $355.4 million, or 4.7%, to $7,985.6 million, or 30.9% of total assets, as of June 30, 2026, from $7,630.2 million, or 28.6% of total assets, as of December 31, 2025. The increase was primarily resulting from purchases of investment securities, partially offset by pay-downs, maturities, called securities, and a $33.9 million decrease in fair market values during the period. 49 Table of Contents As of June 30, 2026 and December 31, 2025, the estimated duration of our investment portfolio was 3.2 and 3.3 years, respectively. As of June 30, 2026 and December 31, 2025, we had $5,078.3 million and $5,645.8 million, respectively, of investment securities that had been in a continuous loss position for more than twelve months. Gross unrealized losses on these securities totaled $462.1 million as of June 30, 2026, and were attributable to changes in interest rates. At June 30, 2026 and December 31, 2025, the Company had no allowance for credit losses on available-for-sale securities and an allowance for credit losses on held-to-maturity securities classified as corporate and municipal securities of $0.1 million and $0.5 million, respectively. Loans Held for Investment, Net of Deferred Fees and Costs Loans held for investment, net of deferred fees and costs, decreased $920.2 million to $14,281.4 million as of June 30, 2026 as compared to $15,201.6 million as of December 31, 2025. The following table presents the composition and comparison of loans held for investment for the periods indicated: June 30, 2026 December 31, 2025 $ Change % Change Real estate: Commercial $ 7,947.9 $ 8,144.4 $ (196.5) (2.4) % Construction 576.1 837.2 (261.1) (31.2) Residential 2,044.7 2,108.8 (64.1) (3.0) Agricultural 592.1 629.0 (36.9) (5.9) Total real estate 11,160.8 11,719.4 (558.6) (4.8) Consumer: Indirect 369.0 477.5 (108.5) (22.7) Direct and advance lines 125.3 131.5 (6.2) (4.7) Total consumer 494.3 609.0 (114.7) (18.8) Commercial 2,275.6 2,359.6 (84.0) (3.6) Agricultural 357.3 520.2 (162.9) (31.3) Other, including overdrafts 1.4 1.7 (0.3) (17.6) Deferred loan fees and costs (8.0) (8.3) 0.3 (3.6) Loans held for investment, net of deferred loan fees and costs $ 14,281.4 $ 15,201.6 $ (920.2) (6.1) The Company discontinued accepting applications to originate indirect loans during the first quarter of 2025, which resulted in $108.5 million of continued amortization for the indirect portfolio as of June 30, 2026. The Company sold $64.1 million of loans related to the sale of the eleven Nebraska branches during the second quarter of 2026. The remaining decline in loan balances is due to loan paydowns and payoffs during the first half of 2026. Non-Performing Assets Non-performing assets include non-performing loans and OREO. Non-Performing Loans. Non-performing loans include non-accrual loans and loans contractually past due 90 days or more and still accruing interest. Non-accrual loans. We generally place loans on non-accrual status when they become 90 days past due unless they are well secured and in the process of collection or if the collection of principal and interest is in doubt. When a loan is placed on non-accrual status, any interest previously accrued but not collected is reversed from income. Non-accrual loans increased approximately $24.9 million, or 18.7%, to $158.4 million as of June 30, 2026, from $133.5 million as of December 31, 2025, primarily due to a single client relationship comprised of commercial and commercial real estate loans. As of June 30, 2026, there were approximately $55.5 million of non-accrual loans for which there was no related allowance for credit losses, as these loans had sufficient collateral securing the loan for repayment. Loans contractually past due 90 days or more and still accruing interest. Loans past due 90 days or more accruing interest were $1.3 million as of June 30, 2026 compared to $1.4 million as of December 31, 2025. 50 Table of Contents Other Real Estate Owned (OREO). OREO consists of real property acquired through foreclosure on the collateral underlying defaulted loans. We record OREO at fair value less estimated selling costs. Any excess of loan carrying value over the fair value of the real estate at the time it is acquired, is recorded as a charge against the allowance for credit losses. Estimated losses that result from the ongoing periodic valuation of these properties are charged to earnings in the period in which they are identified. OREO increased $1.9 million, or 55.9%, to $5.3 million as of June 30, 2026, from $3.4 million as of December 31, 2025. The following table sets forth information regarding non-performing assets as of the dates indicated: Non-Performing Assets (Dollars in millions) June 30, 2026 December 31, 2025 Non-performing loans: Non-accrual loans $ 158.4 $ 133.5 Accruing loans past due 90 days or more 1.3 1.4 Total non-performing loans 159.7 134.9 OREO 5.3 3.4 Total non-performing assets $ 165.0 $ 138.3 Non-accrual loans to loans held for investment 1.11 % 0.88 % Non-performing assets to loans held for investment and OREO 1.15 0.91 Non-performing assets to total assets 0.64 0.52 Allowance for credit losses to non-performing loans 114.09 141.88 The following table sets forth the allocation of our non-performing loans among our various loan categories as of the dates indicated. Non-Performing Loans by Loan Type (Dollars in millions) June 30, 2026 Percent of Total December 31, 2025 Percent of Total Real estate: Commercial $ 60.0 37.7 % $ 35.9 26.6 % Construction 4.7 2.9 4.3 3.2 Residential 12.5 7.8 14.0 10.4 Agricultural 21.6 13.5 27.1 20.1 Total real estate 98.8 61.9 81.3 60.3 Consumer Indirect 4.2 2.6 5.7 4.2 Direct 0.7 0.4 0.7 0.5 Total consumer 4.9 3.0 6.4 4.7 Commercial 38.2 23.9 22.6 16.8 Agricultural 17.8 11.2 24.6 18.2 Total non-performing loans $ 159.7 100.0 % $ 134.9 100.0 % Allowance for Credit Losses The Company performs a quarterly assessment of the appropriateness of its allowance for credit losses in accordance with GAAP. The allowance for credit losses is established through a provision for credit losses based on our evaluation of quantitative and qualitative risk factors in our loan portfolio at each balance sheet date. In determining the allowance for credit losses, we estimate losses on specific loans, or groups of loans, where the expected loss can be identified and reasonably determined over the life of the loans. The balance of the allowance for credit losses is based on internally assigned risk classifications of loans, historical loan loss rates, changes in the nature or tenure of the loan portfolio, overall portfolio quality, industry concentrations, delinquency trends, current environmental and economic factors, and the estimated impact of forecasted economic conditions on historical loan loss rates. 51 Table of Contents The allowance for credit losses is increased by provisions charged against earnings and net recoveries of charged-off loans and is reduced by negative provisions credited to earnings and net loan charge-offs. The allowance for credit losses consists of three elements: (1)A specific valuation allowance associated with collateral-dependent and other individually evaluated loans. Specific valuation allowances are determined based on assessment of the fair value of the collateral underlying the loans as determined through independent appraisals, the present value of future cash flows, observable market prices, and any relevant qualitative or environmental factors impacting loans. (2)A collective valuation allowance based on loan loss experience and future expectations for similar loans with similar characteristics and trends. The Company applies open pool methodologies for all portfolio segments. The open pool methodology averages quarterly loss rates by modeling segment, calculated as quarter-to-date net charge off balance divided by the end of period balance. Loss rates are recalculated quarterly with recoveries captured in the quarter a loan was charged off, are averaged across a look back period from 2009 to the current period, and are annualized. Macroeconomic-conditioned historical loss rates are applied to loan-level cash flows. Expected future principal and interest cash flows are calculated using contractual repayment terms and prepayment, utilization, interest rate, and probability of default assumptions. Macroeconomic sensitivity models calculate segment-specific multipliers using third party forecast data. The multipliers condition the annual loss rates over the 2-year forecast period, followed by a 1-year straight-line reversion to the unadjusted historical average loss rates. The unadjusted loss rates then apply for the remaining life of the loan. Estimated losses are totaled and aggregated to the segment level. (3)A qualitative valuation allowance determined based on asset quality trends, industry concentrations, environmental risks, changes in portfolio composition, and other qualitative risk factors, both internal and external to the Company. Other qualitative factors, including changes in loan and lending policies, collateral quality, underwriting standards and personnel, credit review quality, and model imprecision, are also considered. Based on the assessment of the appropriateness of the allowance for credit losses, the Company records provisions for credit losses to maintain the allowance for credit losses at appropriate levels. Loans acquired in business combinations are initially recorded at fair value as adjusted for credit risk. For loans with no significant evidence of credit deterioration since origination, the difference between the fair value and the unpaid principal balance of the loan at the acquisition date is amortized into interest income using the effective interest method over the remaining period to contractual maturity. An allowance for credit losses is recorded for the expected credit losses over the life of the loan. Subsequent changes to the allowance for credit losses are recorded through provision expense using the same methodology as other loans held for investment. For loans acquired in business combinations with evidence of deterioration in credit quality since origination, the Company determines the fair value of the loans by estimating the amount and timing of principal and interest cash flows initially expected to be collected on the loans and discounting those cash flows at an appropriate market rate of interest. An allowance for credit losses is recognized by estimating the expected credit losses of the purchased asset and recording an adjustment to the acquisition date fair value to establish the initial amortized cost basis of the asset. Differences between the established amortized cost basis, and the unpaid principal balance of the asset, are considered to be a non-credit discount/premium and is accreted/amortized into interest income using the level yield interest method. Subsequent changes to the allowance for credit losses are recorded through provision expense using the same methodology as other loans held for investment. Loans, or portions thereof, are charged-off against the allowance for credit losses when management believes the collectability of the principal is unlikely, or, with respect to consumer installment loans, according to an established delinquency schedule. Generally, loans are charged-off when (1) there has been no material principal reduction within the previous 90 days and there is no pending sale of collateral or other assets, (2) there is no significant or pending event which will result in principal reduction within the upcoming 90 days, (3) it is clear that we will not be able to collect all or a portion of the loan, or (4) foreclosure or repossession actions are pending. Loan charge-offs do not directly correspond with the receipt of independent appraisals or the use of observable market data if the collateral value is determined to be sufficient to repay the principal balance of the loan. If a collateral-dependent loan is adequately collateralized, a specific valuation allowance for credit losses is not recorded. As such, significant changes in collateral-dependent and non-performing loans do not necessarily correspond proportionally with changes in the specific valuation component of the allowance for credit losses. Additionally, the Company expects the timing of charge-offs will vary between quarters and will not necessarily correspond proportionally 52 Table of Contents to changes in the allowance for credit losses or changes in non-performing or collateral-dependent loans due to timing differences among the initial identification of a collateral-dependent loan, recording of a specific valuation allowance for collateral-dependent loans, and any resulting charge-off of uncollectible principal. Our allowance for credit losses was $182.2 million, or 1.28% of loans held for investment as of June 30, 2026 compared to $191.4 million, or 1.26% of loans held for investment, as of December 31, 2025. The percentage increase reflected changes related to the specific valuation allowance on non-accrual loans, partially offset by changes in the mix of loan balances. The Company’s allowance for off-balance sheet credit losses was $6.9 million as of June 30, 2026, compared to $5.9 million as of December 31, 2025. We have established our allowance for credit losses in accordance with GAAP in the United States and we believe that the allowance for credit losses is appropriate to provide for known and expected losses in the portfolio, future provisions will be subject to on-going evaluations of the risks in the loan portfolio. If the economy declines or asset quality deteriorates, material additional provisions could be required. 53 Table of Contents The following table sets forth information regarding our allowance for credit losses as of the dates and for the periods indicated: Allowance for Credit Losses Three Months Ended Six Months Ended (Dollars in millions) Jun 30, 2026 Dec 31, 2025 Jun 30, 2025 Jun 30, 2026 Jun 30, 2025 Allowance for credit losses on loans: Beginning balance $ 195.8 $ 205.8 $ 215.3 $ 191.4 $ 204.1 (Reduction of) provision for credit losses (3.9) 7.7 0.1 2.9 20.3 Charge-offs: Real estate Commercial 0.4 19.0 2.8 0.4 2.8 Residential 0.5 0.3 0.4 1.0 0.7 Agricultural 0.1 — — 0.1 — Consumer 2.4 3.4 5.6 6.2 10.3 Commercial 2.1 1.7 2.2 4.3 5.1 Agricultural 8.5 0.1 2.0 8.5 4.9 Total charge-offs 14.0 24.5 13.0 20.5 23.8 Recoveries: Real estate Commercial 2.1 0.1 4.8 3.3 4.8 Construction — 0.1 — — — Residential 0.4 0.1 0.2 0.7 0.3 Agricultural — 0.5 0.2 — 0.2 Consumer 1.1 0.8 1.5 2.1 2.7 Commercial 0.6 0.7 0.4 2.1 0.9 Agricultural 0.1 0.1 0.1 0.2 0.1 Total recoveries 4.3 2.4 7.2 8.4 9.0 Net charge-offs 9.7 22.1 5.8 12.1 14.8 Ending balance $ 182.2 $ 191.4 $ 209.6 $ 182.2 $ 209.6 Allowance for off-balance sheet credit losses: Beginning balance $ 5.8 $ 6.3 $ 5.1 $ 5.9 $ 5.2 Provision for (reduction of) off-balance sheet credit losses 1.1 (0.4) (0.3) 1.0 (0.4) Ending balance $ 6.9 $ 5.9 $ 4.8 $ 6.9 $ 4.8 Allowance for credit losses on investment securities: Beginning balance $ 0.5 $ 0.7 $ 0.8 $ 0.5 $ 0.9 Reduction of credit losses on investment securities (0.4) (0.2) (0.1) (0.4) (0.2) Ending balance $ 0.1 $ 0.5 $ 0.7 $ 0.1 $ 0.7 Total allowance for credit losses $ 189.2 $ 197.8 $ 215.1 $ 189.2 $ 215.1 Total (reduction of) provision for credit losses (3.2) 7.1 (0.3) 3.5 19.7 Loans held for investment, net of deferred fees and costs 14,281.4 15,201.6 16,353.4 14,281.4 16,353.4 Average loans 14,524.6 15,540.5 17,053.8 14,776.8 17,359.4 Net loans charged-off to average loans, annualized 0.27 % 0.56 % 0.14 % 0.17 % 0.17 % Allowance to non-accrual loans 115.03 143.37 108.77 115.03 108.77 Allowance to loans held for investment 1.28 1.26 1.28 1.28 1.28 Total Liabilities Total liabilities decreased $631.2 million, or 2.7%, to $22,562.4 million as of June 30, 2026, from $23,193.6 million as of December 31, 2025, primarily due to a decrease in deposits. 54 Table of Contents Deposits Our deposits consist of noninterest bearing and interest bearing demand, savings, individual retirement, and time deposit accounts. Total deposits decreased $647.0 million, or 2.9%, to $21,441.3 million as of June 30, 2026, from $22,088.3 million as of December 31, 2025, with decreases across all interest bearing deposit categories. The following table summarizes our deposits as of the dates indicated: Deposits (Dollars in millions) June 30, 2026 Percent of Total December 31, 2025 Percent of Total Noninterest bearing demand $ 5,312.0 24.8 % $ 5,286.8 23.9 % Interest bearing: Demand 6,143.7 28.7 6,319.7 28.6 Savings 7,785.4 36.3 7,843.5 35.5 Time, $250,000 or more 612.7 2.9 792.9 3.6 Time, other (1) 1,587.5 7.3 1,845.4 8.4 Total interest bearing 16,129.3 75.2 16,801.5 76.1 Total deposits $ 21,441.3 100.0 % $ 22,088.3 100.0 % (1)Included in “Time, other” are IntraFi Network Deposits of $5.6 million and $13.4 million as of June 30, 2026 and December 31, 2025, respectively. Deposit Insurance The deposits of the Bank are insured up to the applicable limits by the DIF of the FDIC, generally up to $250,000 per insured depositor. The Bank pays deposit insurance premiums based on assessment rates established by the FDIC. The estimated amount of deposits in excess of the FDIC insurance limit at June 30, 2026 was $7.9 billion, or 36.9% of total deposits. Estimates of uninsured deposits are based on the methodologies and assumptions used in the Bank’s call reports and do not necessarily reflect an evaluation of all scenarios that potentially would determine the availability of deposit insurance to customer accounts based on FDIC regulations. Capital Resources and Liquidity Management Capital Resources. Stockholders’ equity is influenced primarily by earnings, dividends, sales and redemptions of common stock, and changes in the unrealized holding gains or losses, net of taxes, on available-for-sale investment securities. Stockholders’ equity decreased $124.4 million, or 3.6%, to $3,322.6 million as of June 30, 2026, from $3,447.0 million as of December 31, 2025, due to cash dividends paid, stock repurchases of vested restricted shares tendered in lieu of cash for payment of income tax withholding amounts by participants, stock repurchases as part of the stock repurchase program, and an increase to the unrealized losses on available-for-sale securities through other comprehensive income, partially offset the retention of retained earnings. On August 28, 2025, the board of directors of the Company adopted a new stock repurchase program, pursuant to which the Company has been authorized to repurchase up to $150.0 million worth of its issued and outstanding shares of common stock on or prior to March 31, 2027, which is the expiration date of the program. On January 27, 2026, the board of directors authorized an increase to the repurchase program of an additional $150.0 million, and on July 22, 2026 the board of directors authorized a further increase to the repurchase program of an additional $150.0 million, bringing the total repurchase authorization since August 2025 to $450.0 million. Any repurchased shares will be returned to authorized but unissued shares of common stock, as permitted under applicable Delaware law. During the six months ended June 30, 2026, 4,322,662 shares of common stock were repurchased under the stock repurchase program at a total cost of $152.7 million or at a weighted-average price of $35.32 per share. As of June 30, 2026, following these repurchases, approximately $29.7 million remained available for future purchases under the program. From July 1, 2026 to July 30, 2026, the Company purchased approximately 243 thousand shares of common stock, for a total repurchase of approximately $9.3 million. As of July 30, 2026, following these 2026 repurchases and the January 2026 and July 2026 increases in the authorized aggregate dollar value of shares to be repurchased under the repurchase program, approximately $170.4 million remained available for future purchases under the program. 55 Table of Contents On July 22, 2026, the Company’s board of directors declared a dividend of $0.47 per common share, payable on August 14, 2026, to common stockholders of record as of August 4, 2026. The dividend equates to a 5.3% annual yield based on the $35.40 average closing price of the Company’s common stock as reported on NASDAQ during the second quarter of 2026. As a bank holding company, the Company must comply with the capital requirements established by the Federal Reserve, and our subsidiary Bank must comply with the capital requirements established by the FDIC. The current risk-based guidelines applicable to us and our Bank are based on the Basel III framework, as implemented by the federal bank regulators. As of June 30, 2026 and December 31, 2025, the Company had capital levels that, in all cases, exceeded the guidelines to be deemed “well-capitalized.” For additional information regarding our capital levels, see “Note – Regulatory Capital” in the accompanying “Notes to Unaudited Consolidated Financial Statements” included in this report. Liquidity. Liquidity measures our ability to meet current and future cash flow needs on a timely basis and at a reasonable cost. We manage our liquidity position to meet the daily cash flow needs of clients, while maintaining an appropriate balance between assets and liabilities to meet the return-on-investment objectives of our shareholders. Our liquidity position is supported by management of liquid assets and liabilities and access to alternative sources of funds. Liquid assets include cash, interest bearing deposits in banks, federal funds sold, available-for-sale investment securities, and maturing or prepaying balances in our held-to-maturity investment and loan portfolios. Liquid liabilities include core deposits, federal funds purchased, securities sold under repurchase agreements, and borrowings. Other sources of liquidity include the sale of loans, the ability to acquire additional national market funds through non-core deposits, the issuance of additional collateralized borrowings such as FHLB advances, the issuance of debt securities, additional borrowings through the Federal Reserve’s discount window, and the issuance of preferred or common securities. Our short-term and long-term liquidity requirements are primarily to fund ongoing operations, including payment of interest on deposits and debt, extensions of credit to borrowers, capital expenditures, and shareholder dividends. These liquidity requirements are met primarily through cash flow from operations, redeployment of prepaying and maturing balances in our loan and investment portfolios, the issuance of securities, borrowings and other debt financing, and increases in client deposits. For the six months ended June 30, 2026, net cash provided by operating activities was $112.9 million, net cash provided by investing activities was $420.8 million and net cash used in financing activities was $676.3 million. Major uses of cash were $402.9 million in outflows of deposits. Major sources of cash included $913.0 million in net loan repayments and $532.7 million in investment security maturities and paydowns. Total cash and cash equivalents were $1,167.1 million as of June 30, 2026, compared to $1,309.7 million as of December 31, 2025. For additional information regarding our operating, investing, and financing cash flows, see the unaudited “Consolidated Statements of Cash Flows,” included in Part I – Financial Information, “Item 1 – Financial Statements.” For additional information regarding our deposits, see “–Financial Condition – Deposits,” above. As of June 30, 2026, the Company had $125.0 million of aggregate principal amount of fixed-to-floating rate subordinated notes due June 15, 2035, and available borrowing capacity of $4,977.3 million with the FHLB. The Company has unused federal fund lines of credit with third parties amounting to $235.0 million, subject to funds availability. These lines are subject to cancellation without notice. The Company also has an unused line of credit with the FRB for borrowings up to $5,018.6 million secured by government and agency backed securities and a blanket pledge of agricultural and commercial loans. As of June 30, 2026, the Company sponsored twelve wholly-owned business trusts. The trusts were formed for the exclusive purpose of issuing an aggregate of $149.9 million of 30-year floating rate mandatorily redeemable capital trust preferred securities (“Trust Preferred Securities”) to third-party investors. The Trusts also issued, in aggregate, $4.9 million of common equity securities to First Interstate BancSystem, Inc. Proceeds from the issuance of the Trust Preferred Securities and common equity securities were invested in 30-year junior subordinated deferrable interest debentures (“Subordinated Debentures”) issued by First Interstate BancSystem, Inc. As a holding company, we are a corporation separate and apart from our subsidiary Bank and, therefore, we provide for our own liquidity. Our primary sources of funding include management fees and dividends declared and paid by the Bank and access to capital markets. There are statutory, regulatory, and debt covenant limitations that affect the ability of our Bank to pay dividends to us. Management believes that such limitations will not impact our ability to meet our ongoing short-term cash obligations. The Company continuously monitors our liquidity position and adjustments are made to the balance between sources and uses of funds as deemed appropriate. We are not aware of any events that are reasonably likely to have a material adverse effect on our liquidity, capital resources, or operations. In addition, we are not aware of any regulatory recommendations regarding liquidity, which if implemented, would have a material adverse effect on us. The Bank 56 Table of Contents satisfies incremental liquidity needs with either liquid assets or external funding sources. Available liquidity includes cash, FHLB advances and FRB borrowings through the discount window. The Bank has pledged its investment securities portfolio to access wholesale funding as needed and does not intend to sell or restructure securities at this time. June 30, 2026 December 31, 2025 (Dollars in billions) FHLB FRB Total FHLB FRB Total Total borrowing capacity $ 5.0 $ 5.0 $ 10.0 $ 5.4 $ 3.6 $ 9.0 Borrowings outstanding — — — — — — Remaining Capacity, at period end $ 5.0 $ 5.0 $ 10.0 $ 5.4 $ 3.6 $ 9.0 Cash and due from banks 0.3 0.4 Interest bearing deposits 0.8 1.0 Total available liquidity $ 11.1 $ 10.4 Through the Bank’s relationship with the FHLB, the Bank owns $10.6 million of FHLB stock and has access to additional liquidity and funding sources through FHLB advances. The Bank’s borrowing capacity is dependent upon the amount of collateral the Bank places at the FHLB. Recent Accounting Pronouncements See “Note – Recent Authoritative Accounting Guidance” in the accompanying “Notes to Unaudited Consolidated Financial Statements” included in this report for details of recently issued accounting pronouncements and their expected impact on our financial statements.