Last frost date in Williston, North Dakota
May 21
Average last frost in spring. In an early year (1 in 10) it's over by May 8; in a late year (1 in 10) it comes after June 3.
September 21
Average first frost in fall. 1 year in 10 it comes by September 9.
Source: NOAA U.S. Climate Normals 1991–2020, station Williston Sloulin International AP (USW00094014), 1.2 miles from Williston, elevation 1,902 ft. NOAA National Centers for Environmental Information. These are long-term averages, not a forecast.
| Early year | Average | Late year | |
|---|---|---|---|
| Last frost in spring | May 8 | May 21 | June 3 |
| First frost in fall | Sept 9 | Sept 21 | Oct 2 |
Frost-free days in an average year: 123
| Chance in a year | Average last in spring | Average first in fall | |
|---|---|---|---|
| Light frost (36°F) | Every year | May 29 | Sept 12 |
| Frost (32°F) | Every year | May 21 | Sept 21 |
| Hard freeze (28°F) | Every year | May 11 | Sept 28 |
Nights at 32°F or colder in an average year: 191
What to plant now in Williston
- Spring planting calendar for an average last frost around May 20 Williston: May 21
- Fall planting calendar for an average first frost around September 20 Williston: September 21
Planting dates: USDA Home and Garden Bulletin No. 9 (1967), “Suburban and Farm Vegetable Gardens,” tables 4 and 5. How we match the table.
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