Last spring frost
May 10
Frost Dates for Thompson, ND
First fall frost
Oct 1
Growing season
144 days
Hardiness zone
4a
In an average year around Thompson, ND, the last spring frost (32°F) is about May 10 and the first fall frost is about Oct 1, giving roughly a 144-day growing season. To be safe most years, wait until Apr 28 before setting out tender plants.
Last spring frost
Dates the last frost of spring typically ends. Plant tender crops after the risk has passed for your comfort level.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Jun 1 | May 19 | May 7 |
| Freeze (32°F) | May 24 | May 10 | Apr 28 |
| Hard (28°F) | May 14 | Apr 30 | Apr 16 |
| Severe (24°F) | May 5 | Apr 21 | Apr 6 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Jun 1 | May 29 | May 26 | May 23 | May 19 | May 17 | May 14 | May 12 | May 7 |
| 32°F | May 24 | May 19 | May 16 | May 12 | May 10 | May 7 | May 4 | May 1 | Apr 28 |
| 28°F | May 14 | May 9 | May 5 | May 2 | Apr 30 | Apr 28 | Apr 24 | Apr 21 | Apr 16 |
| 24°F | May 5 | Apr 30 | Apr 27 | Apr 24 | Apr 21 | Apr 18 | Apr 15 | Apr 11 | Apr 6 |
| 20°F | Apr 25 | Apr 21 | Apr 16 | Apr 13 | Apr 10 | Apr 7 | Apr 5 | Apr 2 | Mar 29 |
| 16°F | Apr 17 | Apr 13 | Apr 9 | Apr 6 | Apr 3 | Apr 1 | Mar 30 | Mar 25 | Mar 20 |
First fall frost
Dates the first frost of fall typically arrives. Count back by a crop's days-to-maturity to know your planting cutoff.
| Frost intensity | Early (10%) | Average (50%) | Late (90%) |
|---|---|---|---|
| Light (36°F) | Sep 10 | Sep 23 | Oct 3 |
| Freeze (32°F) | Sep 20 | Oct 1 | Oct 15 |
| Hard (28°F) | Sep 29 | Oct 12 | Oct 25 |
| Severe (24°F) | Oct 7 | Oct 22 | Nov 2 |
Show full probability table (all thresholds & percentiles)
| °F | 10% | 20% | 30% | 40% | 50% | 60% | 70% | 80% | 90% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | Sep 10 | Sep 15 | Sep 18 | Sep 21 | Sep 23 | Sep 25 | Sep 27 | Sep 30 | Oct 3 |
| 32°F | Sep 20 | Sep 24 | Sep 26 | Sep 29 | Oct 1 | Oct 3 | Oct 6 | Oct 10 | Oct 15 |
| 28°F | Sep 29 | Oct 2 | Oct 5 | Oct 9 | Oct 12 | Oct 15 | Oct 18 | Oct 20 | Oct 25 |
| 24°F | Oct 7 | Oct 12 | Oct 16 | Oct 19 | Oct 22 | Oct 24 | Oct 27 | Oct 30 | Nov 2 |
| 20°F | Oct 15 | Oct 21 | Oct 25 | Oct 27 | Oct 30 | Nov 1 | Nov 4 | Nov 7 | Nov 11 |
| 16°F | Oct 25 | Oct 29 | Nov 1 | Nov 4 | Nov 7 | Nov 9 | Nov 12 | Nov 15 | Nov 19 |
Growing season is measured at 32°F with about 50% probability. Hardiness zone from the 2023 USDA map; frost normals from NOAA 1991-2020.
Where this data comes from
@endif These dates are computed from the nearest official weather station with long-term records: Grand Forks Univ (Nws), Nd, about 9.8 miles away@if(!empty($station['elevation_ft'])), at 830 ft elevation. The further the station and the greater the elevation difference from your yard, the more your local frost timing can vary.
How we calculate these dates
Frost and freeze dates come from the NOAA 1991–2020 U.S. Climate Normals, the National Oceanic and Atmospheric Administration's 30-year averages for each weather station. A date shown at the 50% level is the median: in half of years the frost falls on or before it. The 10% and 90% columns show the early and late ends of the range, so you can plant on the odds you're comfortable with. These are long-term averages, not a forecast for this year - always check your local outlook before planting.
Source: NOAA National Centers for Environmental Information, 1991–2020 Climate Normals (public domain). Harman is not affiliated with or endorsed by NOAA.
Frequently asked questions
When is the last frost in Thompson, ND?
On average, the last spring frost (32°F) around Thompson, ND is about May 10. In cooler years it can run later, so for a safer bet many gardeners wait until Apr 28.
When is the first frost in the fall?
The first fall frost around Thompson, ND typically arrives about Oct 1. Count back by a crop's days to maturity to find the latest date you can plant it.
When can I plant tomatoes and other tender crops?
Tender crops like tomatoes, peppers and basil are damaged by frost, so wait until the last spring frost has passed - around May 10 on average, or Apr 28 to be safe most years.
How long is the growing season here?
The frost-free growing season (between the last spring and first fall 32°F frost) is about 144 days in a typical year.
Are these dates a forecast for this year?
No. They are 30-year averages from the NOAA 1991–2020 Climate Normals, not a prediction for the current year. Use them for planning and always check your local weather forecast before planting or protecting crops.
Local weather for 58278 Planting calendar → North Dakota frost dates →
Data source: NOAA 1991–2020 Climate Normals · Page updated Aug 4, 2026