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 |
An early or late year is one in 10: 1 year in 10 the frost comes before the early date, and 1 year in 10 after the late date.
Frost-free days in an average year: 123
Planting calendar for Williston
Fall planting
USDA dates for places whose average first freeze is about September 20 (Williston: September 21).
- Broccoli plantsMay 1 – June 15 (past for this year)
- Brussels sprouts plantsMay 1 – June 15 (past for this year)
- Cabbage plantsMay 1 – June 15 (past for this year)
- Cantaloupe (muskmelon)May 1 – June 15 (past for this year)
- Cauliflower plantsMay 1 – July 1 (past for this year)
- PotatoesMay 1 – June 15 (past for this year)
- WatermelonMay 1 – June 15 (past for this year)
- Celery and celeriac plantsMay 15 – July 1 (past for this year)
- Chervil and chivesMay 15 – June 15 (past for this year)
- Collards plantsMay 15 – June 15 (past for this year)
- ParsnipsMay 15 – June 15 (past for this year)
- Summer squashMay 15 – July 1 (past for this year)
- Witloof chicoryMay 15 – June 15 (past for this year)
- SalsifyMay 20 – June 20 (past for this year)
- Winter squashMay 20 – June 10 (past for this year)
- BeetsJune 1 – July 1 (past for this year)
- CarrotsJune 1 – July 1 (past for this year)
- Chinese cabbageJune 1 – July 1 (past for this year)
- CucumbersJune 1 – 15 (past for this year)
- DandelionJune 1 – July 1 (past for this year)
- Florence fennelJune 1 – July 1 (past for this year)
- Garden peasJune 1 – July 15 (past for this year)
- Head lettuce plantsJune 1 – July 15 (past for this year)
- KaleJune 1 – July 1 (past for this year)
- KohlrabiJune 1 – July 15 (past for this year)
- Leaf lettuceJune 1 – Aug 1 (past for this year)
- Mustard greensJune 1 – Aug 1 (past for this year)
- OkraJune 1 – 20 (past for this year)
- ParsleyJune 1 – July 1 (past for this year)
- Peppers plantsJune 1 – 20 (past for this year)
- RadishesJune 1 – Aug 15 (past for this year)
- RutabagaJune 1 – July 1 (past for this year)
- Snap beansJune 1 – July 1 (past for this year)
- SorrelJune 1 – July 1 (past for this year)
- SpinachJune 1 – Aug 1 (past for this year)
- Sweet cornJune 1 – July 1 (past for this year)
- Swiss chardJune 1 – July 1 (past for this year)
- TomatoesJune 1 – 20 (past for this year)
- TurnipsJune 1 – July 15 (past for this year)
- Corn saladJune 15 – Aug 1 (past for this year)
- EndiveJune 15 – July 15 (past for this year)
- Upland cressJune 15 – Aug 1 (past for this year)
- Rhubarb plantsSept 15 – Nov 1Now
USDA lists garlic, horseradish, leeks, onion plants, onion seed, onion sets, shallots as generally spring-planted here.
Spring planting
USDA dates for places whose average last freeze is about May 20 (Williston: May 21).
- SpinachApr 10 – June 15
- Chervil and chivesApr 15 – May 15
- Corn saladApr 15 – June 1
- DandelionApr 15 – May 15
- Garden peasApr 15 – June 1
- GarlicApr 15 – May 15
- PotatoesApr 15 – June 15
- RadishesApr 15 – June 15
- Rhubarb plantsApr 15 – May 10
- TurnipsApr 15 – June 1
- Asparagus plantsApr 20 – May 15
- Horseradish plantsApr 20 – May 20
- KaleApr 20 – May 10
- KohlrabiApr 20 – May 20
- Onion plants plantsApr 20 – May 15
- Onion seedApr 20 – May 15
- Onion setsApr 20 – May 15
- ShallotsApr 20 – May 10
- BeetsApr 25 – June 15
- Broccoli plantsMay 1 – June 15
- Brussels sprouts plantsMay 1 – June 15
- Cabbage plantsMay 1 – June 15
- CarrotsMay 1 – June 1
- Chinese cabbageMay 1 – June 15
- Collards plantsMay 1 – June 1
- EndiveMay 1 – 30
- Florence fennelMay 1 – 30
- Head lettuce plantsMay 1 – June 30
- Leaf lettuceMay 1 – June 30
- LeeksMay 1 – 20
- Mustard greensMay 1 – June 30
- ParsleyMay 1 – 20
- ParsnipsMay 1 – 20
- RutabagaMay 1 – 20
- SalsifyMay 1 – June 1
- SorrelMay 1 – June 1
- Upland cressMay 1 – June 1
- Cauliflower plantsMay 10 – June 15
- Celery and celeriac plantsMay 10 – June 15
- Swiss chardMay 10 – June 15
- Snap beansMay 15 – June 30
- Sweet cornMay 15 – June 1
- New Zealand spinachMay 20 – June 15
- Summer squashMay 20 – June 15
- Peppers plantsMay 25 – June 15
- TomatoesMay 25 – June 15
- CucumbersJune 1 – 15
- Eggplant plantsJune 1 – 15
- OkraJune 1 – 20
- Witloof chicoryJune 1 – 15
- WatermelonJune 15 – July 1
Planting dates: USDA Home and Garden Bulletin No. 9 (1967), “Suburban and Farm Vegetable Gardens,” tables 4 and 5 (earliest safe spring and latest safe fall dates), applied to this place's NOAA frost dates. “Plants” means setting out transplants, not sowing seed. How we match the table.