Boise Weather in September

Boise in the Treasure Valley has a semi-arid climate with hot, dry summers and cool winters. The city is in a rain shadow east of the Cascade-Sierra Nevada mountain chain, receiving only about 12 inches of precipitation annually. The Boise River and Greenbelt provide riparian cooling, while hot and dry conditions in summer can lead to significant wildfire smoke events from regional fires.

Excellent shoulder season — warm with fewer tourists in many destinations.