Last updated: June 24, 2025
In December, the average temperature in Rapid City, United States hovers around -2°C (28°F), with fluctuations that can see lows of -19°C (-3°F) and highs reaching 15°C (58°F). Expect 74 mm (2.9 in) of precipitation spread over approximately 16 days, paired with a high average humidity of 87%. Stay prepared for a chilly and damp month!
In December in Rapid City, the average temperature is -2°C (28°F). Maximum temperatures can reach 15°C (58°F), while minimums can drop as low as -19°C (-3°F). Travelers should be prepared for a wide range of temperatures, ensuring they pack appropriately for chilly weather as well as milder conditions.
In Rapid City in December, the total precipitation amount is 74 mm (2.9 in) spread over 16 days.
In Rapid City in December, humidity is 87%. With an average temperature of -2°C (28°F), this humidity feels like a damp chill that seeps into your bones, making outdoor exploration less enjoyable and requiring extra layers to stay warm and comfortable while traveling.
In Rapid City in December, the maximum UV index is 2, which corresponds to a low exposure category. With this level of UV radiation, the time to burn is approximately 45 minutes. To learn more about the hourly UV index in Rapid City, you can visit Hourly UV Index in Rapid City.
UV Risk Categories
Weather in Rapid City varies notably across the year, with each month offering distinct climate conditions. This page compares December’s weather to other months in Rapid City, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -6°C (22°F) | 57 mm (2.2 inches) | 91% | low |
| February Weather | -6°C (22°F) | 62 mm (2.4 inches) | 91% | moderate |
| March Weather | -1°C (31°F) | 62 mm (2.4 inches) | 87% | moderate |
| April Weather | 5°C (42°F) | 97 mm (3.8 inches) | 87% | high |
| May Weather | 13°C (56°F) | 119 mm (4.7 inches) | 82% | very high |
| June Weather | 19°C (66°F) | 111 mm (4.4 inches) | 79% | very high |
| July Weather | 21°C (71°F) | 103 mm (4.1 inches) | 75% | very high |
| August Weather | 20°C (68°F) | 91 mm (3.6 inches) | 76% | very high |
| September Weather | 16°C (61°F) | 78 mm (3.1 inches) | 79% | high |
| October Weather | 10°C (49°F) | 131 mm (5.2 inches) | 83% | moderate |
| November Weather | 2°C (35°F) | 77 mm (3.0 inches) | 86% | moderate |
| December Weather | -2°C (28°F) | 74 mm (2.9 inches) | 87% | low |