Last frost date in Watertown, South Dakota
May 7
Average last frost in spring. In an early year (1 in 10) it's over by April 26; in a late year (1 in 10) it comes after May 20.
September 30
Average first frost in fall. 1 year in 10 it comes by September 19.
Source: NOAA U.S. Climate Normals 1991–2020, station Watertown Rgnl AP (USW00014946), 0.4 miles from Watertown, elevation 1,748 ft. NOAA National Centers for Environmental Information. These are long-term averages, not a forecast.
| Early year | Average | Late year | |
|---|---|---|---|
| Last frost in spring | Apr 26 | May 7 | May 20 |
| First frost in fall | Sept 19 | Sept 30 | Oct 13 |
Frost-free days in an average year: 145
| Chance in a year | Average last in spring | Average first in fall | |
|---|---|---|---|
| Light frost (36°F) | Every year | May 17 | Sept 23 |
| Frost (32°F) | Every year | May 7 | Sept 30 |
| Hard freeze (28°F) | Every year | Apr 29 | Oct 9 |
Nights at 32°F or colder in an average year: 174
What to plant now in Watertown
- Spring planting calendar for an average last frost around May 10 Watertown: May 7
- Fall planting calendar for an average first frost around September 30 Watertown: September 30
Planting dates: USDA Home and Garden Bulletin No. 9 (1967), “Suburban and Farm Vegetable Gardens,” tables 4 and 5. How we match the table.