On January 11, 2023, Ross E. Leckie notified First Interstate BancSystem, Inc. (the “Company”) that for personal reasons he was resigning as a Director of the Company effective at midnight on January 12, 2023. His resignation is not related to any disagreement with the Company on any matter relating to the Company’s operations, policies, or practices. Mr. Leckie has been a valuable member of the Company’s Board of Directors for more than a decade, and the Company thanks him for his dedicated service and many contributions to the Company and wishes him well.

Following the announcement of Mr. Leckie’s resignation, Frances P. Grieb, a current member of the Audit Committee of the Board of Directors who has also been determined by the Board of Directors to qualify as an audit committee financial expert under applicable rules of the Securities and Exchange Commission, has graciously agreed to replace Mr. Leckie on an interim basis as the Chair of the Company’s Audit Committee.