Weather history and climate summary information is available for the following locations:
- Billings
- Glasgow
- Great Falls
- Helena
- Lewistown
- Miles City
- Missoula
Warmest December Days
The warmest December days in Montana are:
| Billings, Montana | 1980 | 69.1°F |
| Billings, Montana | 1990 | 66°F |
| Lewistown, Montana | 1988 | 66°F |
| Billings, Montana | 1999 | 64.9°F |
| Billings, Montana | 2004 | 64.9°F |
Coldest December Days
The coldest December days in Montana were:
| Lewistown, Montana | 1983 | -42.2°F |
| Great Falls, Montana | 1983 | -42°F |
| Miles City, Montana | 1989 | -40.2°F |
| Glasgow, Montana | 1977 | -38°F |
| Glasgow, Montana | 1989 | -38°F |
Wettest December Days
The wettest single days in December occurred:
| Lewistown, Montana | 1984 | 2.1 inches |
| Great Falls, Montana | 2006 | 1.9 inches |
| Great Falls, Montana | 1973 | 0.9 inches |
| Billings, Montana | 1973 | 0.8 inches |
| Missoula, Montana | 1996 | 0.8 inches |