August in Rapid City averages a daily high of 28.9°C with nights around 15.7°C. Expect roughly 8.9 wet days totalling 54.6mm. Comfortable conditions for being outdoors all day.
Across the year, the best time to visit Rapid City is September.
Based on RAPID CITY WEATHER FORECAST OFFICE, SD US (1.8km), 1995–2024. 29 years of August data.