When Is the Last Frost in North Dakota?
The average last spring frost in North Dakota falls between May 6 and May 19 for most ZIP codes, with a statewide median of May 12. At the average date a later frost is still a coin flip, so tender plants wait for the safer 90% date.
| City | Last frost | 90% safe after | First frost | Growing season |
|---|---|---|---|---|
| Fargo | May 4 | May 18 | Oct 2 | 151 days |
| Bismarck | May 10 | May 23 | Sep 30 | 142 days |
| Grand Forks | May 10 | May 24 | Oct 1 | 144 days |
| Minot | May 10 | May 22 | Oct 1 | 144 days |
| West Fargo | May 10 | May 23 | Sep 30 | 143 days |
| Williston | May 13 | May 25 | Sep 26 | 135 days |
| Dickinson | May 20 | Jun 1 | Sep 22 | 123 days |
| Mandan | May 10 | May 23 | Sep 30 | 142 days |
| Jamestown | May 11 | May 24 | Sep 28 | 138 days |
| Wahpeton | May 4 | May 17 | Oct 3 | 152 days |
| Devils Lake | May 12 | May 24 | Sep 30 | 141 days |
| Valley City | May 13 | May 25 | Sep 26 | 136 days |
| Watford City | May 9 | May 22 | Sep 27 | 139 days |
| Grafton | May 4 | May 18 | Oct 7 | 156 days |
| Beulah | May 21 | Jun 3 | Sep 20 | 121 days |
| New Town | May 20 | Jun 2 | Sep 20 | 121 days |
| Rugby | May 17 | May 31 | Sep 23 | 129 days |
| Stanley | May 17 | May 29 | Sep 23 | 127 days |
Last and first frost: 50% (median) dates of the last spring and first fall 32 °F night. 90% safe after: only a 10% chance of a later spring frost. First frost dates in January fall in the following winter. Each city uses the NOAA station nearest the ZIP code closest to its center.
Across all 125 North Dakota weather stations with frost records, median last frost dates run from May 2 at Hillsboro 3 N, ND to May 24 at Hettinger Muni AP, ND. Elevation, valleys that collect cold air and distance from large water bodies explain most of the spread, so a garden a few miles from a listed city can differ by a week or more. The ZIP code lookup above uses the same NOAA data as the frost date calculator for every US ZIP code.
When Is the First Frost in North Dakota?
The average first fall frost in North Dakota arrives between September 22 and October 3 for most ZIP codes, with a median of September 28. Tomatoes, peppers, basil and squash are damaged at 32 °F, so harvest or cover them before then.
Fall frost can come early: Fargo has a 10% chance of frost before September 22, Bismarck has a 10% chance of frost before September 16 and Grand Forks has a 10% chance of frost before September 20. Hardy crops such as kale, spinach and cabbage tolerate light frosts and keep producing after the first frost date.
When to Plant Tomatoes in North Dakota?
Transplant tomatoes in North Dakota 1 to 2 weeks after the local average last frost, once nights stay above about 50 °F: May 11 – May 18 in Fargo, May 17 – May 24 in Bismarck and May 17 – May 24 in Grand Forks. Start seeds indoors 6 to 8 weeks before the last frost.
| City | Start seeds indoors | Transplant outdoors | Lowest-risk transplant |
|---|---|---|---|
| Fargo | Mar 9 – Mar 23 | May 11 – May 18 | after May 18 |
| Bismarck | Mar 15 – Mar 29 | May 17 – May 24 | after May 23 |
| Grand Forks | Mar 15 – Mar 29 | May 17 – May 24 | after May 24 |
| Minot | Mar 15 – Mar 29 | May 17 – May 24 | after May 22 |
| West Fargo | Mar 15 – Mar 29 | May 17 – May 24 | after May 23 |
| Williston | Mar 18 – Apr 1 | May 20 – May 27 | after May 25 |
| Dickinson | Mar 25 – Apr 8 | May 27 – Jun 3 | after Jun 1 |
| Mandan | Mar 15 – Mar 29 | May 17 – May 24 | after May 23 |
| Jamestown | Mar 16 – Mar 30 | May 18 – May 25 | after May 24 |
| Wahpeton | Mar 9 – Mar 23 | May 11 – May 18 | after May 17 |
| Devils Lake | Mar 17 – Mar 31 | May 19 – May 26 | after May 24 |
| Valley City | Mar 18 – Apr 1 | May 20 – May 27 | after May 25 |
| Watford City | Mar 14 – Mar 28 | May 16 – May 23 | after May 22 |
| Grafton | Mar 9 – Mar 23 | May 11 – May 18 | after May 18 |
| Beulah | Mar 26 – Apr 9 | May 28 – Jun 4 | after Jun 3 |
| New Town | Mar 25 – Apr 8 | May 27 – Jun 3 | after Jun 2 |
| Rugby | Mar 22 – Apr 5 | May 24 – May 31 | after May 31 |
| Stanley | Mar 22 – Apr 5 | May 24 – May 31 | after May 29 |
Indoors: 6–8 weeks before the average last frost. Outdoors: 1–2 weeks after it. Lowest-risk: after the date with only a 10% chance of a later frost. Rules of thumb; check the 10-day forecast and wait for soil near 60 °F.
Tomatoes stall below about 50 °F at night and are killed by frost, so a week or two of waiting after the average date costs little. The tomato plant care guide covers light, watering and feeding once plants are in the ground.
What Can You Plant in Fargo and When?
Fargo's average last frost of May 4 anchors its spring planting calendar: peas and spinach go in from March 23, broccoli and lettuce transplants from April 6, and tomatoes, peppers and squash after May 11.
| Crop | Start seeds indoors | Plant outdoors | Frost tolerance |
|---|---|---|---|
| Peas | — | Mar 23 – Apr 6direct sow, 4–6 weeks before last frost | hardy |
| Spinach | — | Mar 23 – Apr 13direct sow, 3–6 weeks before last frost | hardy |
| Radishes | — | Mar 30 – Apr 13direct sow, 3–5 weeks before last frost | hardy |
| Onions (sets) | — | Apr 6 – Apr 20plant, 2–4 weeks before last frost | hardy |
| Potatoes | — | Apr 6 – Apr 20plant, 2–4 weeks before last frost | half-hardy |
| Broccoli & cabbage | Mar 9 – Mar 23 | Apr 6 – Apr 20transplant, 2–4 weeks before last frost | hardy |
| Lettuce | Mar 23 – Apr 6 | Apr 6 – Apr 20transplant, 2–4 weeks before last frost | hardy |
| Beets | — | Apr 6 – Apr 20direct sow, 2–4 weeks before last frost | half-hardy |
| Carrots | — | Apr 13 – Apr 20direct sow, 2–3 weeks before last frost | half-hardy |
| Tomatoes | Mar 9 – Mar 23 | May 11 – May 18transplant, 1–2 weeks after last frost | tender |
| Basil | Mar 9 – Mar 23 | May 11 – May 25transplant, 1–3 weeks after last frost | tender |
| Peppers | Feb 23 – Mar 9 | May 18 – May 25transplant, 2–3 weeks after last frost | tender |
| Eggplant | Feb 23 – Mar 9 | May 18 – May 25transplant, 2–3 weeks after last frost | tender |
| Green beans | — | May 11 – May 25direct sow, 1–3 weeks after last frost | tender |
| Sweet corn | — | May 11 – May 25direct sow, 1–3 weeks after last frost | tender |
| Cucumbers | Apr 6 – Apr 13 | May 11 – May 25transplant, 1–3 weeks after last frost | tender |
| Squash & zucchini | Apr 6 – Apr 13 | May 11 – May 25transplant, 1–3 weeks after last frost | tender |
| Watermelon | Apr 6 – Apr 13 | May 18 – May 25transplant, 2–3 weeks after last frost | tender |
Dates for Fargo (last frost May 4, NOAA station Fargo 3 S, ND, 2 miles from ZIP 58103). General rules of thumb; wait for soil near 50 °F for most seeds and 60 °F for beans, corn and squash.
How Long Is the Growing Season in North Dakota?
The frost-free growing season in North Dakota lasts about 124 to 151 days for most ZIP codes, with a median of 138 days. Among the listed cities, Beulah has the shortest season at 121 days and Grafton the longest at 156.
Season length decides which varieties ripen: compare it with the “days to maturity” on seed packets, counted from transplanting for tomatoes and peppers. NOAA stations in North Dakota range from 115 days at Hettinger Muni AP, ND to 158 days at Hillsboro 3 N, ND. Planning beds before the season starts helps in short seasons — a plant spacing calculator for vegetable beds shows how many transplants fit.
What Hardiness Zones Are in North Dakota?
North Dakota spans USDA hardiness zones 3b to 4b, with zone 4a the most common. Zones describe winter cold and decide which perennials survive, while frost dates set when to plant annual vegetables and flowers.
The North Dakota planting zone map with the zone of each city shows how the zones are spread across the state and which plants are hardy in all of them.
Frequently Asked Questions
- When is the last frost in North Dakota?
- The average last spring frost in North Dakota falls between May 6 and May 19 for most ZIP codes, with a statewide median of May 12. Among major cities it ranges from May 4 in Fargo to May 21 in Beulah.
- When is the last frost in Fargo, North Dakota?
- Fargo's average last spring frost is May 4, and by May 18 the chance of a later frost drops to 10%. Its first fall frost averages October 2, giving a 151-day growing season (NOAA station Fargo 3 S, ND).
- When should you plant tomatoes in North Dakota?
- Transplant tomatoes in North Dakota 1 to 2 weeks after the local average last frost, once nights stay above about 50 °F: May 11 – May 18 in Fargo, May 17 – May 24 in Bismarck and May 17 – May 24 in Grand Forks. Start seeds indoors 6 to 8 weeks before the last frost.
- When is the first frost in North Dakota?
- The average first fall frost in North Dakota arrives between September 22 and October 3 for most ZIP codes, with a median of September 28. Harvest tender crops such as tomatoes, peppers and basil before then or cover them on cold nights.
- How long is the growing season in North Dakota?
- The frost-free growing season in North Dakota lasts about 124 to 151 days for most ZIP codes, with a median of 138 days, from 121 days in Beulah to 156 days in Grafton.
Frost data: NOAA National Centers for Environmental Information, 1991–2020 U.S. Climate Normals (32 °F freeze dates by probability). ZIP code and city locations and populations: U.S. Census Bureau Gazetteer files and Vintage 2024 population estimates. Planting windows are general rules of thumb. PlantoScan is not affiliated with or endorsed by these agencies.