Cheyenne, like most of the rest of Wyoming, is semi-arid (Köppen BSk). Winters are cold and moderately long, but relatively dry, with a January average of 25.9 °F (−3.4 °C), highs that fail to reach freezing occur 37 days per year, and lows dip to the 0 °F (−18 °C) mark on 12 nights. However, the coldness is often interrupted, with chinook winds blowing down slope from the Rockies that can bring warm conditions, bringing the high above 50 °F (10 °C) on 20 days from December to February. Snowfall is greatest in March and April, averaging 60 inches (152 cm) for the season; yet thick snow cover rarely stays. Summers are warm, with a July average of 67.7 °F (19.8 °C), and highs reaching 90 °F (32 °C) 8 times. Spring and autumn are quick transitions, with the median freeze dates being May 12 and September 26. The annual precipitation tends to be concentrated from May to August and is low during fall and winter, contributing to the area's 2980 hours (~68%) of the possible total, of sunshine per year
