Last updated: June 24, 2025
In September, the average temperature in Rapids City, United States hovers around 20°C (69°F), creating a pleasant atmosphere. Expect temperature fluctuations with a minimum of 5°C (41°F) and a maximum reaching 34°C (94°F). This month also brings 107 mm (4.2 in) of precipitation over approximately 10 days, contributing to an average humidity of 78%.
In September in Rapids City, the average temperature is 20°C (69°F). Maximums can reach 34°C (94°F), while minimums can drop as low as 5°C (41°F). This makes Rapids City a suitable destination for travelers looking to experience mild weather with the possibility of warmer days.
In Rapids City in September, the precipitation amount is 107 mm (4.2 in) accumulated over a period of 10 days.
In Rapids City in September, humidity is 78%. With an average temperature of 20°C (69°F), this humidity feels like a warm, enveloping blanket, making travel somewhat uncomfortable as sweat clings to your skin and the air feels thick and heavy, urging you to seek out shaded areas and refreshing drinks.
In Rapids City in September, the maximum UV index is 8, which corresponds to a very high Exposure Category. This means that the time to burn is only 15 minutes. For more detailed information, you can refer to the Hourly UV Index in Rapids City.
UV Risk Categories
Weather in Rapids City varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Rapids City, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -4°C (24°F) | 55 mm (2.2 inches) | 81% | moderate |
| February Weather | -3°C (27°F) | 59 mm (2.3 inches) | 81% | moderate |
| March Weather | 5°C (40°F) | 93 mm (3.6 inches) | 81% | high |
| April Weather | 10°C (50°F) | 109 mm (4.3 inches) | 82% | very high |
| May Weather | 17°C (63°F) | 149 mm (5.9 inches) | 78% | very high |
| June Weather | 23°C (74°F) | 137 mm (5.4 inches) | 81% | extreme |
| July Weather | 25°C (77°F) | 88 mm (3.5 inches) | 79% | very high |
| August Weather | 23°C (74°F) | 73 mm (2.9 inches) | 77% | very high |
| September Weather | 20°C (69°F) | 107 mm (4.2 inches) | 78% | very high |
| October Weather | 12°C (55°F) | 120 mm (4.7 inches) | 78% | high |
| November Weather | 4°C (39°F) | 50 mm (2.0 inches) | 87% | moderate |
| December Weather | 0°C (33°F) | 49 mm (1.9 inches) | 84% | low |