Precipitation in May comes mostly in showers. By June, thunderstorms are a common occurrence. The storms form over the Black Hills almost every afternoon and move onto the Plains during the evening. June marks the peak of severe weather season. Flash flooding and large hail are the most common hazards.
Tornadoes are infrequent and weak.
Despite all the moisture, Rapid City sees an average of 20 clear to partly cloudy days and 65 percent of its possible sunshine. Temperatures warm as summer approaches. Daytime highs in May average in the 60s and 70s during June. Overnight temperatures are still chilly, especially in Black Hills communities, where May minimums are in the 30s and 40s. Lows are typically in the 40s and 50s during June.