When to plant in Williston, ND
USDA Zone 4aHere are the average frost dates, USDA hardiness zone, and a month-by-month planting calendar for Williston, North Dakota — all computed from Williston's nearest NOAA weather station.
Zone 4a is cold — in Williston, most perennials must be fully hardy, and your frost dates set a tight window for tender annual vegetables.
Frost probability
WILLISTON SLOULIN INTL AP · 1991–2020The date the last spring and first fall frost occur, by threshold and probability. A 90% date is later in spring — and earlier in fall — than a 10% date; the 50% · 32°F row is what most gardeners plan around. These are Williston’s own odds, recorded at WILLISTON SLOULIN INTL AP.
| Threshold | SPRING 10% | SPRING 50% | SPRING 90% | FALL 10% | FALL 50% | FALL 90% |
|---|---|---|---|---|---|---|
| 36°F | Jun 16 | May 29 | May 18 | Sep 1 | Sep 12 | Sep 23 |
| 32°F | Jun 3 | May 21 | May 8 | Sep 9 | Sep 21 | Oct 2 |
| 28°F | May 25 | May 11 | Apr 29 | Sep 16 | Sep 28 | Oct 11 |
Download this table as CSV ↓ — every threshold and probability, plus this city’s planting-window dates.
What to plant now
TODAY · JULY 19Full-year planting calendar
Each bar is the exact window to take a planting action in Williston, drawn to the day from the local frost dates. The dashed line is today.
Nearby weather stations
2 within 9 km · complete 32°F normalsWhen stations disagree by more than a few days, that spread is real microclimate variation — elevation, water, urban heat. Judge which station best matches your own yard.
Williston planting FAQ
When is the last spring frost in Williston, ND?
On average, the last spring frost in Williston is around May 21 (50% probability at 32°F, from 1991–2020 NOAA normals). Wait until after this date to set out tender plants like tomatoes and peppers.
When is the first fall frost in Williston, ND?
In Williston, the first 32°F freeze of fall lands around September 21 on average. Time your last harvests and any season-extension cover before it.
What hardiness zone is Williston in?
Williston is in USDA hardiness zone 4a. In zone 4a, winters are cold — pick cold-hardy varieties and protect tender crops.
How long is the growing season in Williston?
There are roughly 123 frost-free days in Williston (a short growing season), running from the average last frost around May 21 to the first fall frost near September 21.
When should I plant tomatoes in Williston?
In Williston, start tomato seeds indoors around March 26–April 9, then transplant seedlings outdoors around May 28 once the danger of frost has passed.
Never miss a window in Williston
An email when it’s time to start seeds, transplant, and sow — timed to Williston’s frost dates. Double opt-in, one-click unsubscribe, no spam.
Nearby cities
8 within reachFrost dates recorded at WILLISTON SLOULIN INTL AP, 2 km from the city center · 1991–2020 NOAA climate normals · zone from the USDA/PRISM 2023 map. How we compute this.
BlissGarden. "When to Plant in Williston, ND — Frost Dates & Zone 4a." Frost normals: NOAA NCEI U.S. Climate Normals 1991–2020, station USW00094014. Retrieved from https://blissgarden.com/north-dakota/williston.