Weather history and climate summary information is available for the following locations:
- Bellingham
- Grant County Airport
- Seattle
- Spokane
- Tacoma
- Walla Walla
- Yakima
Warmest May Days
The warmest May days in Washington are:
| Yakima, Washington | 1986 | 102°F |
| Grant County Airport, Washington | 1987 | 102°F |
| Grant County Airport, Washington | 1983 | 100.9°F |
| Yakima, Washington | 1983 | 100.9°F |
| Grant County Airport, Washington | 1986 | 100.9°F |
Coldest May Days
The coldest May days in Washington were:
| Spokane, Washington | 2002 | 24.1°F |
| Grant County Airport, Washington | 2010 | 25°F |
| Yakima, Washington | 1986 | 25°F |
| Spokane, Washington | 1954 | 25°F |
| Spokane, Washington | 1984 | 25°F |
Wettest May Days
The wettest single days in May occurred:
| Spokane, Washington | 1980 | 7 inches |
| Seattle, Washington | 1973 | 6.3 inches |
| Spokane, Washington | 1973 | 5.9 inches |
| Yakima, Washington | 1973 | 5.5 inches |
| Bellingham, Washington | 1977 | 4.3 inches |