Weather history and climate summary information is available for the following locations:
- Huron
- Rapid City
- Sioux Falls
- Watertown
Warmest May Days
The warmest May days in South Dakota are:
| Watertown, South Dakota | 1948 | 120.2°F |
| Huron, South Dakota | 2009 | 98.1°F |
| Rapid City, South Dakota | 1939 | 97.3°F |
| Rapid City, South Dakota | 1969 | 97°F |
| Sioux Falls, South Dakota | 2009 | 95°F |
Coldest May Days
The coldest May days in South Dakota were:
| Watertown, South Dakota | 1948 | 0.3°F |
| Huron, South Dakota | 1976 | 14°F |
| Huron, South Dakota | 2005 | 18°F |
| Rapid City, South Dakota | 1996 | 18.9°F |
| Huron, South Dakota | 1981 | 18.9°F |
Wettest May Days
The wettest single days in May occurred:
| Rapid City, South Dakota | 2008 | 5.3 inches |
| Sioux Falls, South Dakota | 1973 | 5.1 inches |
| Sioux Falls, South Dakota | 2004 | 4.4 inches |
| Huron, South Dakota | 1990 | 3.5 inches |
| Huron, South Dakota | 2007 | 2.9 inches |