First Interstate BancSystem Safe Harbor Page 2 This presentation 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, and Rule 3b-6 promulgated thereunder, that involve inherent risks and uncertainties. Any statements about our plans, objectives, expectations, strategies, beliefs, or future performance or events constitute forward-looking statements. 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. Such forward-looking statements include but are not limited to statements about revenues, income from the origination and sale of loans, net interest margin, quarterly provisions for loan losses, non-interest expense, loan growth, non-performing assets and net charge-off of loans, the benefits of the business combination transaction involving First Interstate BancSystem, Inc. (FIBK) and Mountain West Financial Corp (MTWF), including future financial and operating results, the combined company’s plans, objectives, expectations and intentions, and other statements that are not historical facts. These forward-looking statements are subject to risks and uncertainties that may cause actual results to differ materially from those projected, including but not limited to the following: the factors described in our Form 10-K and subsequent filings with the Securities and Exchange Commission (“SEC”), including under the sections entitled “Risk Factors,” the possibility that the merger does not close when expected or at all because required regulatory, shareholder or other approvals and other conditions to closing are not received or satisfied on a timely basis or at all; the risk that the benefits from the transaction may not be fully realized or may take longer to realize than expected, including as a result of changes in general economic and market conditions, interest and exchange rates, monetary policy, laws and regulations and their enforcement, and the degree of competition in the geographic and business areas in which FIBK and MTWF operate; the ability to promptly and effectively integrate the businesses of FIBK and MTWF; the reaction of the companies’ customers, employees and counterparties to the transaction; and the diversion of management time on merger-related issues. The risk factors described in Forms 10-K 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 the forward-looking statement contained in this presentation. Other unknown or unpredictable factors also could affect 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. 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. Additional Information About the Merger and Where to Find it FIBK intends to file with the SEC a proxy statement/prospectus and other relevant materials in connection with the merger, including the definitive merger agreement. The proxy statement/prospectus will be mailed to the shareholders of MTWF. Investors are urged to read the proxy statement/prospectus and the other relevant materials when they become available because they will contain important information about MTWF, FIBK and the merger. The proxy statement/prospectus and other relevant materials (when they become available), and any other documents filed by FIBK with the SEC, may be obtained free of charge at the SEC’s web site at www.sec.gov. In addition, investors may obtain free copies of the documents filed by FIBK with the SEC by contacting Amy Anderson, First Interstate BancSystem, Inc., 401 N. 31st Street, Billings, MT, 59101; telephone 406-255-5390. | 
