Weather history and climate summary information is available for the following locations:
- Casper
- Cheyenne
- Sheridan
Warmest September Days
The warmest September days in Wyoming are:
| Sheridan, Wyoming | 1998 | 100.9°F |
| Sheridan, Wyoming | 2007 | 99°F |
| Sheridan, Wyoming | 1978 | 99°F |
| Sheridan, Wyoming | 1979 | 99°F |
| Sheridan, Wyoming | 1990 | 98.1°F |
Coldest September Days
The coldest September days in Wyoming were:
| Sheridan, Wyoming | 1984 | 6.1°F |
| Cheyenne, Wyoming | 1985 | 8.1°F |
| Casper, Wyoming | 1983 | 16°F |
| Casper, Wyoming | 1985 | 17.1°F |
| Cheyenne, Wyoming | 1984 | 17.1°F |
Wettest September Days
The wettest single days in September occurred:
| Cheyenne, Wyoming | 1973 | 2.7 inches |
| Casper, Wyoming | 1973 | 1.9 inches |
| Casper, Wyoming | 1950 | 1.8 inches |
| Casper, Wyoming | 1989 | 1.8 inches |
| Sheridan, Wyoming | 1999 | 1.5 inches |