By Susan Sanders, Rapid City NOAA Office
Sunny, mild days and cool nights are typical during the autumn. Temperatures begin to cool around Labor Day, with highs averaging in the 60s and 70s during September and 50s and 60s in October. Lows drop from the 30s and 40s to the 20s and 30s.
Precipitation changes from rain to snow during this time. The first significant snowfall of the season is usually in October, although higher elevations often receive snow in September. The northern Hills average a foot of snow in October, while the southern Hills receive a couple of inches. Occasional cold fronts moving through the area can bring blustery northwest winds.
November and December mark the beginning of winter in the Black Hills, while January has the coldest average temperatures during the year. Despite cooler temperatures and more snow; the area still has many mild, sunny days.
Daytime temperatures in December and January are in the 20s and 30s, with nighttime readings between 10 and 20 above zero. Below zero temperatures are not uncommon in the higher elevations of the Black Hills. Occasionally, cold air from Canada will bring a brief spell of subzero temperatures to the entire area. Unlike areas to the east, where the bitterly cold air remains for several days, warmer weather returns quickly to the Black Hills. Chinook winds can raise temperatures into the 50s and 60s.
Monthly snowfall averages from five inches on the plains to 20 inches in the Hills. Storms earlier in the season tend to bring more moisture from the south, which produces wet, heavy snow. As the winter progresses, storm tracks are from the west and northwest, bringing powdery snow. The snow on the plains usually melts a couple of days after it falls, but deeper snow in the northern Black Hills lasts through the season into spring.