Last updated: June 24, 2025
In September, the average temperature in Casper, United States hovers around 16°C (60°F), but be prepared for a wide range of temperatures—minimums can drop to -9°C (16°F), while maximums can soar to 35°C (96°F). Expect 29 mm (1.2 in) of precipitation spread over 6 days, with humidity levels averaging around 72%. Whether you're planning outdoor adventures or cozy indoor activities, this month offers a mix of weather conditions to consider!
In September in Casper, the average temperature is 16°C (60°F). The maximum can reach 35°C (96°F), while the minimum can drop as low as -9°C (16°F). Be prepared for a wide range of temperatures when traveling to Casper this month.
In Casper in September, the total precipitation amount is 29 mm (1.2 in) over the course of 6 days.
In Casper in September, humidity is 72%. With an average temperature of 16°C (60°F), this humidity feels like a warm, damp blanket enveloping you as you travel, making it essential to stay hydrated and take breaks in shaded areas to enjoy your journey comfortably.
In Casper in September, the maximum UV index is 9, which corresponds to a very high Exposure Category. The time to burn is just 15 minutes, so it's essential to take precautions. For detailed information, you can check the Hourly UV Index in Casper.
UV Risk Categories
Weather in Casper varies notably across the year, with each month offering distinct climate conditions. This page compares September’s weather to other months in Casper, focusing on differences in temperature, rainfall, humidity, and UV levels.
| Temperature | Precipitation | Humidity | UV | |
|---|---|---|---|---|
| January Weather | -6°C (21°F) | 23 mm (0.9 inches) | 79% | moderate |
| February Weather | -7°C (19°F) | 31 mm (1.2 inches) | 81% | high |
| March Weather | -1°C (31°F) | 48 mm (1.9 inches) | 70% | high |
| April Weather | 3°C (38°F) | 59 mm (2.3 inches) | 67% | extreme |
| May Weather | 10°C (50°F) | 70 mm (2.7 inches) | 70% | very high |
| June Weather | 18°C (65°F) | 30 mm (1.2 inches) | 75% | extreme |
| July Weather | 22°C (72°F) | 17 mm (0.7 inches) | 76% | extreme |
| August Weather | 21°C (69°F) | 19 mm (0.7 inches) | 76% | extreme |
| September Weather | 16°C (60°F) | 29 mm (1.2 inches) | 72% | very high |
| October Weather | 5°C (41°F) | 43 mm (1.7 inches) | 70% | high |
| November Weather | 1°C (34°F) | 26 mm (1.0 inches) | 76% | moderate |
| December Weather | -5°C (24°F) | 27 mm (1.1 inches) | 81% | moderate |