BKH

• The merger agreement was entered into on August 18, 2025, and approved by both boards; the transaction is subject to regulatory approvals including state commissions and FERC.
• Exhibit 99.1 includes NorthWestern's unaudited condensed consolidated financial statements for the six months ended June 30, 2026 and 2025.
• Exhibit 99.2 includes unaudited pro forma condensed combined financial statements as if the merger were completed on January 1, 2025 (income statement) and June 30, 2026 (balance sheet).
• The pro forma information is illustrative only and does not purport to project future results of the combined company.

8.01 Other Events · 9.01 Financial Statements and Exhibits

• Adjusted earnings for Q2 2026 were $41.5 million, or $0.54 per diluted share, excluding $0.04 per share of merger-related costs.
• Year-to-date 2026 GAAP EPS was $2.23, and adjusted EPS was $2.33, excluding $0.10 per share of merger-related costs.
• The company reaffirmed 2026 adjusted EPS guidance of $4.25 to $4.45, excluding merger-related costs.
• The merger with NorthWestern Energy is expected to close by year-end 2026, pending final approval from the Montana Public Service Commission.

2.02 Results of Operations and Financial Condition · 9.01 Financial Statements and Exhibits

• The merger agreement, entered into August 18, 2025, is an all-stock business combination between Black Hills and NorthWestern, approved by both boards.
• The filing includes NorthWestern's unaudited financial statements for the three months ended March 31, 2026, showing net income of $63.5 million on revenues of $497.6 million.
• Pro forma combined financial statements are presented as if the merger closed on January 1, 2025 (income statement) and March 31, 2026 (balance sheet).
• The merger remains subject to regulatory approvals, including state commissions and the Federal Energy Regulatory Commission.

8.01 Other Events · 9.01 Financial Statements and Exhibits

• Adjusted EPS (non-GAAP) for Q1 2026 was $1.79, excluding $0.05 per share of merger-related costs, compared to $1.87 in Q1 2025.
• Revenue for Q1 2026 was $780.7 million, down from $805.2 million in Q1 2025.
• The company reaffirmed 2026 adjusted EPS guidance of $4.25 to $4.45, excluding merger-related costs and mark-to-market adjustments.
• Black Hills received shareholder approval for its merger with NorthWestern Energy and expects closing in the second half of 2026.

2.02 Results of Operations and Financial Condition · 9.01 Financial Statements and Exhibits

• Annual Meeting of Shareholders held April 29, 2026, with a quorum present.
• Shareholders ratified Deloitte & Touche LLP as independent registered public accounting firm for 2026 (66,181,234 for, 1,028,970 against).
• Advisory, non-binding approval of named executive officer compensation passed (59,589,296 for, 1,096,350 against).
• Report filed under Item 5.07 to disclose final voting results.

5.07 Submission of Matters to a Vote of Security Holders

• Shareholders approved the issuance of Black Hills common stock in the merger (59,799,414 for, 1,463,912 against).
• Shareholders approved amending Black Hills' articles to increase authorized shares from 100 million to 300 million and to change the company name.
• Shareholders authorized an increase in Black Hills' authorized indebtedness from $8 billion to $20 billion.
• The merger remains subject to regulatory approvals (Hart-Scott-Rodino, FERC, and state approvals in Montana, Nebraska, and South Dakota) and is expected to close in the second half of 2026.

5.07 Submission of Matters to a Vote of Security Holders · 7.01 Regulation FD Disclosure · 9.01 Financial Statements and Exhibits

• Black Hills Corporation filed an 8-K on February 19, 2026, to provide historical financial statements of NorthWestern Energy Group and pro forma combined financial information related to their pending merger.
• The merger agreement was signed on August 18, 2025, and provides for an all-stock business combination of Black Hills and NorthWestern.
• Exhibit 99.2 contains unaudited pro forma combined condensed financial statements as if the merger were completed on January 1, 2025 (income statement) and December 31, 2025 (balance sheet).
• The merger remains subject to conditions including Hart-Scott-Rodino clearance, shareholder approvals, and regulatory approvals from state commissions and FERC.

8.01 Other Events · 9.01 Financial Statements and Exhibits

• Full-year 2025 GAAP EPS was $3.98, and adjusted EPS was $4.10, excluding $0.12 per share of merger-related costs; adjusted EPS increased about 5% from $3.91 in 2024.
• The company initiated 2026 adjusted EPS guidance of $4.25 to $4.45, reflecting 6% growth over 2025, excluding merger-related costs and mark-to-market adjustments.
• Black Hills completed its 260-mile, $350 million Ready Wyoming electric transmission expansion project in December 2025, with about $300 million of investment recovered through a rider as of Jan. 1, 2026.
• The pending all-stock merger with NorthWestern Energy is expected to close in the second half of 2026, with shareholder votes scheduled for April 2, 2026.
• The company approved a quarterly dividend of $0.703 per share, marking 56 consecutive years of dividend increases.

2.02 Results of Operations and Financial Condition · 9.01 Financial Statements and Exhibits