Union Pacific Corp., the No.1 U.S. railroad, forecast third-quarter profit below analysts' expectations as mild summer weather and flooding in Colorado hurt coal shipments.

Shares of the company fell 1.6 percent in extended trading.

An uncertain economic environment continued to impact intermodal volumes, Union Pacific said in a statement on Thursday.

The company said it expects profit of $2.45-$2.48 per share for the quarter ending September. Analysts on average had expected a profit of $2.56 per share, according to Thomson Reuters I/B/E/S.

Union Pacific, which links 23 states in the West and Midwest, also forecast a $10 million hit to operating income related to the flooding.

Shares of the company closed at $155.38 on the New York Stock Exchange on Thursday.