Last updated: June 24, 2025
In September, the average temperature in Rapid City, United States hovers around 16°C (61°F). Prepare for a range that can dip to a chilly 0°C (32°F) and soar to a warm 34°C (93°F). Be ready for some rain, as 78 mm (3.1 in) of precipitation is expected over approximately 11 days. Don't forget, the average humidity during this time is a high 79%, making it an interesting month to experience!
In September in Rapid City, the average temperature is 16°C (61°F). Maximums can reach 34°C (93°F), while minimums can drop to as low as 0°C (32°F). This diverse temperature range makes Rapid City a great destination for travelers seeking both warm and cool experiences during their visit.
In Rapid City in September, the precipitation amount is 78 mm (3.1 in) over the course of 11 days.
In Rapid City in September humidity is 79%. With an average temperature of 16°C (61°F), this humidity feels like a warm, moist embrace, making travel a bit more challenging as the air tends to weigh heavily, but it also offers a refreshing atmosphere perfect for exploring local sights and enjoying nature.
In Rapid City in September, the maximum UV index is 7, which corresponds to the high Exposure Category. This means that the time to burn is approximately 25 minutes. For more detailed information, you can check the 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 September’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 |