Cheyenne, like most of the rest of Wyoming, has a continental semi-arid climate and is part of USDA Hardiness zone 5b, with the suburbs falling in zone 5a. Winters are cold and moderately long, but relatively dry, having a normal mean temperature of 27.7 °F (−2.4 °C), highs that fail to breach freezing for 35 days per year, and lows that dip to the 0 °F (−18 °C) mark on 9.2 mornings. However, the cold is often interrupted, with chinook winds blowing downslope from the Rockies that can bring warm conditions, bringing the high above 50 °F (10 °C) on twenty days from December to February.
While December is the coldest month, snowfall is greatest in March and April, seasonally averaging 60 inches (1,500 mm), historically ranging from 13.1 inches (330 mm) between July 1965 and June 1966 up to 121.5 inches (3,090 mm) between July 1979 and June 1980, yet thick snow cover rarely stays. Summers are warm, with a high diurnal temperature range; July averages 69.4 °F (20.8 °C), and highs reach 90 °F (32 °C) on average for twelve afternoons annually. Spring and autumn are quick transitions, with the average window for freezing temperatures being September 29 thru May 14, allowing a growing season of 106 days. Official record temperatures range from −38 °F (−39 °C) on January 9, 1875, up to 100 °F (38 °C) on June 23, 1954, the last of four occurrences; the record cold daily maximum is −21 °F (−29 °C) on January 11, 1963, while, conversely, the record warm daily minimum is 68 °F (20 °C) on July 31, 1960. The annual precipitation of 15.9 inches (400 mm) tends to be concentrated from May to August and is low during fall and winter; it has historically ranged from 5.04 inches (128.0 mm) in 1876 to 23.69 inches (602 mm) in 1942.
The city averages below 60% daily relative humidity in each month and receives an average 2,980 hours (~67% of the possible total) of sunshine annually. On July 16, 1979, an F3 tornado struck Cheyenne, causing one death and 40 injuries. It was the most destructive tornado in Wyoming history.