Click on a day for an hourly weather forecast
The temperatures in Casper in September are quite cold with temperatures between 9°C and 22°C, warm clothes are a must.
You can expect about 3 to 8 days of rain in Casper during the month of September. It’s a good idea to bring along your umbrella so that you don’t get caught in poor weather.
Please note that Casper can expect a few days of snow in September.
Our weather forecast can give you a great sense of what weather to expect in Casper in September 2025.
If you’re planning to visit Casper in the near future, we highly recommend that you review the 14 day weather forecast for Casper before you arrive.
| Month | Temperatures | Rainy Days | Dry Days | Snowy Days | Rainfall | Weather | More details |
|---|---|---|---|---|---|---|---|
| January | -1° / -12° | 5 | 12 | 14 | 37 mm | Awful | Casper in January |
| February | -1° / -12° | 6 | 6 | 17 | 51 mm | Awful | Casper in February |
| March | 6° / -6° | 6 | 11 | 14 | 72 mm | Awful | Casper in March |
| April | 9° / -3° | 6 | 10 | 14 | 92 mm | Bad | Casper in April |
| May | 15° / 3° | 9 | 14 | 8 | 99 mm | Bad | Casper in May |
| June | 23° / 9° | 4 | 25 | 1 | 49 mm | Perfect | Casper in June |
| July | 28° / 13° | 2 | 29 | 0 | 40 mm | Perfect | Casper in July |
| August | 27° / 13° | 2 | 29 | 0 | 38 mm | Perfect | Casper in August |
| September | 22° / 9° | 3 | 26 | 1 | 37 mm | Good | Casper in September |
| October | 12° / 0° | 3 | 19 | 8 | 61 mm | Bad | Casper in October |
| November | 6° / -5° | 5 | 14 | 11 | 35 mm | Awful | Casper in November |
| December | -1° / -11° | 7 | 10 | 14 | 45 mm | Awful | Casper in December |