December in Rapid City averages a daily high of 3.3°C with nights around -7.5°C. Expect roughly 5.3 wet days totalling 9.5mm. A hard month to visit for comfort alone.
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 December data.