Great Falls, MT Weather

Great Falls has a cold semi-arid climate , with a notable amount of summer precipitation occurring in the form of thunderstorms. Winters are very cold, long and often snowy, though periods of chinook winds do cause warm spells and raise the maximum temperature above 50 °F or 10 °C on an average of fifteen afternoons during the three-month winter period. In the absence of such winds, shallow cold snaps are common; there is an average of 20.8 nights with a low of 0 °F (−17.8 °C) or colder and 44 days failing to top freezing. The wettest part of the year is the spring. Summers are hot and dry, with highs reaching 90 °F (32.2 °C) on nineteen days per year, though the diurnal temperature variation is large and easily exceeds 30 °F (16.7 °C). Freak early and late summer snowfalls such as a two-day total of 8.3 in (0.21 m) in August 1992 can occur, although the median snowfall from June to September is zero and on average the window for accumulating (0.1 in or 0.25 cm) snowfall is October 2–May 13. The average first and last freeze dates are September 21 and May 21, respectively, allowing a growing season of 122 days, although, excepting for July, a freeze has occurred in every month of the year. Extreme temperatures range from −49 °F (−45.0 °C) on February 15, 1936 to 107 °F (41.7 °C) on July 25, 1933.