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To the Shareholders of FIRST INTERSTATE BANCSYSTEM INC CL A,

The 2026 Annual Meeting of Shareholders of FIRST INTERSTATE BANCSYSTEM INC CL A will be held on May 27, 2026 for Shareholders of record as of April 02, 2026.

Your vote is important, so please vote at your earliest convenience.

To Request Paper Copies of Materials

If you are a shareholder of record who received a Notice of Availability of Proxy Materials, and wish to elect to receive a paper copy of the proxy materials, please visit the following site: Request FIRST INTERSTATE BANCSYSTEM INC CL A Proxy Materials.

Alternatively, you may request a hardcopy of the proxy materials via e-mail at info@astfinancial.com or phone at 1-888-Proxy-NA (1-888-776-9962) or 1-718-921-8562. Be sure to include your control number in the e-mail.

If you own shares through a broker, please follow the instructions that were provided to you by your broker/financial institution.

If you have any questions, please contact AST.

Thank You,

Equiniti Trust Company, LLC

Transfer Agent for FIRST INTERSTATE BANCSYSTEM INC CL A