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Frost Dates in North Dakota
First and last frost dates across North Dakota, computed from 68 NOAA weather stations (1991–2020 climate normals). Your exact date depends on your city and microclimate — use the ZIP lookup on the main tool for a station-specific answer.
Last spring frost
May 13
statewide median · range May 3–May 22
First fall frost
Sep 27
statewide median · range Sep 17–Oct 5
Growing season
136 days
median · range 119–155
Stations used
68
NOAA 1991–2020 normals
Frost dates by city
Median dates from the nearest NOAA station to each city. The "cautious" date is the 10% spring value — planting after it means only a ~10% chance of a later frost.
| City | Nearest station | Last spring frost | First fall frost | Growing season | Safe transplant |
|---|---|---|---|---|---|
| Fargo | Fargo Hector Intl Ap · 3 mi | May 10 (cautious: May 23) | Sep 30 | 143 days | May 24 |
| Bismarck | Bismarck · 3 mi | May 14 (cautious: May 27) | Sep 27 | 136 days | May 28 |
| Grand Forks | Grand Forks Univ (Nws) · 3 mi | May 10 (cautious: May 24) | Oct 1 | 144 days | May 24 |
How frost varies across North Dakota
Spring frost timing spans about 19 days across the state. Enderlin in southeastern North Dakota typically sees its last spring frost around May 3, while Watford City in western North Dakota doesn't clear frost until about May 22. Within any city, low spots and valleys run colder than the station average; areas near buildings and pavement run warmer.
When to plant in North Dakota
As a rule of thumb, cool-season crops (lettuce, peas, spinach) can go in 2–4 weeks before your last spring frost; warm-season transplants (tomatoes, peppers) should wait about 2 weeks after it — around May 27 for the statewide median. Check your city's row above rather than the statewide median: a 19-day statewide spread makes the city-level date the one that matters.
These are climate normals (what's typical), not forecasts. For the current year, watch the 10-day forecast around your planting date.
How this is computed
Statewide medians are the median of the 68 NOAA stations' median frost dates — half the stations run earlier, half later. City rows use the nearest station with 30-year freeze records. Dates are 32°F freeze probabilities from NOAA NCEI 1991–2020 U.S. Climate Normals; nothing is estimated or interpolated.
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Frequently asked questions
When is the last frost date in North Dakota?
The statewide median last spring frost is May 13, but it ranges from May 3 to May 22 depending on where in the state you are. Use your city's row in the table above, or the ZIP lookup on the main tool, for a station-specific date.
When can I plant tomatoes outside in North Dakota?
Warm-season transplants like tomatoes should wait about two weeks after your last spring frost — around May 27 for the statewide median. Your city may differ by weeks; check the "safe transplant" column in the city table.
How long is the growing season in North Dakota?
The median growing season across 68 NOAA stations is 136 days, ranging from 119 to 155 days by location.
Why do frost dates vary so much within North Dakota?
Frost timing follows latitude, elevation, and local terrain. Across North Dakota, last spring frost dates span about 19 days — from around May 3 near Enderlin to May 22 near Watford City. Microclimates (low spots, valleys, urban heat) shift dates further at the garden level.
Where does this data come from?
All frost dates are computed from the NOAA National Centers for Environmental Information 1991–2020 U.S. Climate Normals freeze data (public domain), using each station's 32°F freeze probability statistics. No dates are estimated or interpolated.