Weather history and climate summary information is available for the following locations:
- Billings
- Glasgow
- Great Falls
- Helena
- Lewistown
- Miles City
- Missoula
Warmest September Days
The warmest September days in Montana are:
| Miles City, Montana | 1998 | 103.6°F |
| Billings, Montana | 1983 | 102.9°F |
| Miles City, Montana | 2007 | 102.9°F |
| Glasgow, Montana | 1983 | 102.9°F |
| Miles City, Montana | 2005 | 102°F |
Coldest September Days
The coldest September days in Montana were:
| Glasgow, Montana | 1995 | 15.1°F |
| Great Falls, Montana | 2000 | 16°F |
| Lewistown, Montana | 1984 | 17.1°F |
| Lewistown, Montana | 1985 | 17.1°F |
| Lewistown, Montana | 1983 | 18°F |
Wettest September Days
The wettest single days in September occurred:
| Glasgow, Montana | 1978 | 1.9 inches |
| Miles City, Montana | 1986 | 1.9 inches |
| Great Falls, Montana | 1978 | 1.7 inches |
| Lewistown, Montana | 1978 | 1.7 inches |
| Miles City, Montana | 1991 | 1.6 inches |