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UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
WASHINGTON, D.C. 20549

FORM 8-K

CURRENT REPORT

Pursuant to Section 13 or 15(d) of the Securities Exchange Act of 1934

Date of Report (Date of earliest event reported): Nov. 5, 2025

Black Hills Corporation

(Exact name of Registrant as Specified in Its Charter)

South Dakota | 001-31303 | 46-0458824
(State or Other Jurisdiction of Incorporation) | (Commission File Number) | (IRS Employer Identification No.)
7001 Mount Rushmore Road |
Rapid City, South Dakota |  | 57702
(Address of Principal Executive Offices) |  | (Zip Code)

Registrant’s Telephone Number, Including Area Code: 605 721-1700

(Former Name or Former Address, if Changed Since Last Report)

Check the appropriate box below if the Form 8-K filing is intended to simultaneously satisfy the filing obligation of the registrant under any of the following provisions:

☒Written communications pursuant to Rule 425 under the Securities Act (17 CFR 230.425)

☐Soliciting material pursuant to Rule 14a-12 under the Exchange Act (17 CFR 240.14a-12)

☐Pre-commencement communications pursuant to Rule 14d-2(b) under the Exchange Act (17 CFR 240.14d-2(b))

☐Pre-commencement communications pursuant to Rule 13e-4(c) under the Exchange Act (17 CFR 240.13e-4(c))

Securities registered pursuant to Section 12(b) of the Act:

Title of each class |  | Trading Symbol(s) |  | Name of each exchange on which registered
Common stock of $1.00 par value |  | BKH |  | The New York Stock Exchange

Indicate by check mark whether the registrant is an emerging growth company as defined in Rule 405 of the Securities Act of 1933 (§ 230.405 of this chapter) or Rule 12b-2 of the Securities Exchange Act of 1934 (§ 240.12b-2 of this chapter).

Emerging growth company ☐

If an emerging growth company, indicate by check mark if the registrant has elected not to use the extended transition period for complying with any new or revised financial accounting standards provided pursuant to Section 13(a) of the Exchange Act. ☐

## Item 2.02 Results of Operations and Financial Condition.

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On Nov. 5, 2025, Black Hills Corporation ("the Company") issued a press release announcing financial results for the third quarter of 2025.

The press release is attached as Exhibit 99.1 to this Form 8-K. A copy of the Company's presentation is attached as Exhibit 99.2 to this report. This information is being furnished pursuant to Item 2.02 of Form 8-K and shall not be deemed to be "filed" for the purposes of Section 18 of the Securities Exchange Act of 1934, as amended, or otherwise subject to the liabilities of that section, nor shall it be deemed incorporated by reference in any filing under the Securities Act of 1933, as amended, except as shall be expressly set forth by specific reference in such filing.

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## Item 9.01 Financial Statements and Exhibits.

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Exhibit No. |  | Description
99.1 |  | Press Release dated Nov. 5, 2025
99.2 |  | Presentation dated Nov. 6, 2025
104 |  | Cover Page Interactive Data File (formatted as the inline XBRL document)

SIGNATURES

Pursuant to the requirements of the Securities Exchange Act of 1934, the registrant has duly caused this report to be signed on its behalf by the undersigned hereunto duly authorized.

|  |  | BLACK HILLS CORPORATION
Date: | Nov. 5, 2025 | By: | /s/ Kimberly F. Nooney
|  |  | Kimberly F. Nooney Senior Vice President and Chief Financial Officer