September in Rapid City averages a daily high of 24°C with nights around 10.9°C. Expect roughly 6.9 wet days totalling 35.9mm. 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 September data.