Spring around the Black Hills is cool. Daytime highs in May average in the 60s and warm into the 70s during June. Overnight temperatures are still chilly—especially in the Hills, where May lows are in the 30s and 40s. Lows are typically in the 40s and 50s during June.
Rain showers are frequent during the spring, when the area receives much of its annual precipitation. By June, thunderstorms are a common occurrence. Despite the moisture, Rapid City sees an average of 20 clear to partly-cloudy days per month and 65 percent of its possible sunshine.
Summer time in South Dakota is characterized by sunny, warm days and cool nights. July and August are the warmest months of the year, when daytime temperatures can range from the 70s in the Black Hills to the 90s on the plains. Occasionally, temperatures rise above 100 degrees.
Humidity levels are low—and there is usually a breeze during the day—so even the hottest days are still comfortable. Rapid City receives 75 percent of its possible sunshine. With the Black Hills elevations between 4,000 and 7,000 feet, protection from the intense afternoon sun is a necessity.
Early mornings are cool, so a jacket or sweater may be needed for outdoor activities. Low temperatures average in the 50s, although 40s occur at the higher elevations.
Thunderstorms are an almost-daily occurrence over the Black Hills. They usually produce only brief showers during the afternoon and evening. Severe thunderstorms are most likely during June and July; some produce large hail and strong wind gusts, but tornadoes are infrequent and weak. Rainfall decreases as summer draws to a close: Rapid City reports an average of 9 days in August with thunderstorms, but rainfall is only 1.67 inches. The drier conditions increase the potential for wildfires both in the Black Hills and on the prairies.
Severe Weather Safety
Lightning occurs with every thunderstorm. If you are outdoors in an open area, watch for developing thunderstorms. Don't stand under a tall, isolated tree or on a ridgetop.
The best protection from severe thunderstorms is a sturdy shelter away from windows. If a tornado warning is issued, go to an interior room on the lowest floor. If you are outdoors or in a vehicle and cannot reach a shelter, lie in a ditch or ravine.
The steep canyons, rock cliffs, and small creeks of the Black Hills are prone to flash flooding, especially if thunderstorms contain heavy rain or persist over the same area for a long time. Be cautious when camping near a creek bed—even if it is dry. If heavy rain begins or the creek starts to rise, go to higher ground immediately before you are trapped by rapidly-moving water.
Many of the communities around the Black Hills use warning sirens for severe weather. If you hear them, tune to NOAA Weather Radio or a local radio or TV station for additional information.
For current weather forecasts, warnings, & conditions while you're visiting the Black Hills, local NOAA Weather Radio frequencies are:
Northern Black Hills: Terry Peak 162.525 MHz
Central Black Hills: Rapid City 162.550 MHz
Southern Black Hills: Hot Springs 162.425 MHz
Badlands: Philip 162.450 MHz
Pine Ridge: Porcupine: 162.500 MHz