Weather history and climate summary information is available for the following locations:
- Billings
- Glasgow
- Great Falls
- Helena
- Lewistown
- Miles City
- Missoula
Warmest May Days
The warmest May days in Montana are:
| Glasgow, Montana | 1988 | 102°F |
| Miles City, Montana | 1988 | 100°F |
| Glasgow, Montana | 1980 | 99°F |
| Miles City, Montana | 1984 | 98.1°F |
| Miles City, Montana | 2001 | 97°F |
Coldest May Days
The coldest May days in Montana were:
| Great Falls, Montana | 2009 | 12°F |
| Lewistown, Montana | 2009 | 16°F |
| Lewistown, Montana | 2002 | 16°F |
| Great Falls, Montana | 2005 | 17.1°F |
| Lewistown, Montana | 2005 | 17.1°F |
Wettest May Days
The wettest single days in May occurred:
| Helena, Montana | 1979 | 5.5 inches |
| Glasgow, Montana | 1973 | 5.5 inches |
| Billings, Montana | 1973 | 5.5 inches |
| Miles City, Montana | 1995 | 5 inches |
| Billings, Montana | 2011 | 3.3 inches |