Rapid City, South Dakota - Climate

Climate

Rapid City features a steppe climate (Köppen BSk). Its location makes its climate unlike both the higher elevations of the Black Hills and the Great Plains to the east. It is characterized by long arid summers and long dry winters, with short but distinct spring and autumn seasons.

Winters are cold and dry, with highs averaging from 33.6 °F (0.9 °C) in January; however, Chinook winds can warm temperatures above 50 °F (10 °C), doing so 20 times from December to February. Temperature inversions, however, occasionally produce warmer temperatures in the Black Hills. The January low averages 11.3 °F (−11.5 °C), though it drops below 0 °F (−17.8 °C) on 19 nights per season. Snowfall is greatest in March, with an average 9.1 inches (23.1 cm), and totals 41.1 inches (104 cm) for the season. However, extensive snow cover does not remain for long, with only 9 days per year of 5 inches (13 cm) or more on the ground.

Spring is somewhat gradual, and diurnal temperature ranges begin to become consistently large. May weather is mild and precipitation changes from rain showers to thunderstorms. Storms typically develop over the Black Hills during the afternoon and move onto the plains in the evening. However, Rapid City still sees an average of 20 clear to partly cloudy days and 65 percent of its possible sunshine in June. This is the traditional "flood" season for Rapid and other creeks in the Eastern Hills. Temperatures warm rapidly as summer approaches. Daytime highs range from 62 to 81 °F (17 to 27 °C) in May and June, while the range for lows is 38 to 55 °F (3 to 13 °C).

Summer in Rapid City is hot, relatively dry, and sunny. July and August are the warmest months of the year, when daytime temperatures climb into the mid 80s F (29-30 C), to or above 90 °F (32.2 °C) on an average 29 days per year and 100 °F (37.8 °C) on 3.7 days. Breezy winds and low humidity levels increase heat tolerance. Rapid City records an average of 9 thunderstorm days in August, but only 1.67 inches (42 mm) of rain. Rapid City receives 75 percent of its possible sunshine. Because the elevation of the Black Hills are between 4000 and 8,000 feet (2,400 m), the sun is very intense.

Fall is a precipitous transition season, with sunny, mild days, and cool nights. Highs range from 75 to 53 °F (24 to 12 °C) from mid September to late October, with lows ranging from 46 to 28 °F (8 to -2 °C) in that same time frame. The average first freeze in Rapid City is October 4 and late August through September in the Black Hills. The Rapid City area’s first snowfall is usually in October, although higher elevations sometimes receive significant snow in September. Occasional cold fronts moving through the area bring blustery northwest winds.

November and December mark the beginning of winter in the Black Hills. Despite cooler temperatures and more snow; the area still has many mild, sunny days. By December, daytime temperatures are in the 30s with nighttime readings in the teens and sometimes below zero in the Black Hills. Storms early in the season produce heavy, wet snow. As the winter progresses, storm tracks from the northwest bring drier snow. Rapid City’s chances for a "White Christmas" (defined as having inch or more of snow on the ground) averages about 50 percent.

Sunshine is abundant in the region, averaging 2850 hours, 65% of the possible total, per year.

Rapid City holds two weather records — fastest temperature rise of 49 °F (27 °C) in 2 minutes on January 22, 1943, and fastest temperature drop of 47 °F (26 °C) in 5 minutes on January 10, 1911. Extremes also range from −31 °F (−35 °C) on February 2, 1996, to 110 °F (43 °C) on July 8, 1989.