USDA Hardiness Zone 4a
Frost Dates for 58201 — Grand Forks, North Dakota
NOAA 1991–2020 normals from Grand Forks Univ (NWS), ND (830 ft), 2 miles northwest.
Updated
In Grand Forks, the last spring frost (32°F) is around May 10 in half of years and has passed by May 24 in nine years out of ten. The first fall frost comes around October 1, as early as September 20 one year in ten, leaving a typical freeze-free season of 144 days (NOAA, Grand Forks Univ (NWS), ND).
- Last spring frost
- May 10
- First fall frost
- October 1
- Growing season
- 144 days
- Hardiness zone
- 4a
50% probability
50% probability
freeze-free, 50%
-30 to -25°F (-34.4 to -31.7°C) coldest night
- First snow
- October 31
- Last snow
- April 12
- Winters with snow
- 100%
- Snow per year
- 48.7"
median, 1991–2020
median, 1991–2020
30 of 30 observed
NOAA normal
Frost risk by date in Grand Forks
Half of springs at Grand Forks Univ (NWS), ND see their last 32°F night by May 10; only one in ten is past it by April 28, and one in ten still has one after May 24. Planting tender crops after May 16 leaves a 30% risk of a frost on them, after May 19 20%, and after May 24 10%. The 14 days between the even-odds date and the one-in-ten date is wider than at 82% of the 33 North Dakota stations behind this site's ZIP pages.
In fall the first 32°F night comes by October 1 in half of years, as early as September 20 one year in ten, and holds off past October 15 one year in ten. A hard freeze of 28°F follows 11 days later, around October 12; in spring the one-in-ten date for 28°F is May 14, 10 days before the 32°F one. The freeze-free season lasts 144 days in a typical year, longer than at 82% of the 33 North Dakota stations; it reaches 161 days one year in ten and falls short of 126 one year in ten. On average 179 nights a year drop to 32°F or below. Nights of 36°F, when frost can still settle on leaves in low, open spots, continue 9 days longer, to about May 19, and return around September 23. Severe cold of 16°F or below comes every winter, usually between November 7 and April 3.
| Low | 90% | 80% | 70% | 60% | 50% | 40% | 30% | 20% | 10% |
|---|---|---|---|---|---|---|---|---|---|
| 36°F | May 7 | May 12 | May 14 | May 17 | May 19 | May 23 | May 26 | May 29 | Jun 1 |
| 32°F | Apr 28 | May 1 | May 4 | May 7 | May 10 | May 12 | May 16 | May 19 | May 24 |
| 28°F | Apr 16 | Apr 21 | Apr 24 | Apr 28 | Apr 30 | May 2 | May 5 | May 9 | May 14 |
| 24°F | Apr 6 | Apr 11 | Apr 15 | Apr 18 | Apr 21 | Apr 24 | Apr 27 | Apr 30 | May 5 |
| 20°F | Mar 29 | Apr 2 | Apr 5 | Apr 7 | Apr 10 | Apr 13 | Apr 16 | Apr 21 | Apr 25 |
| 16°F | Mar 20 | Mar 25 | Mar 30 | Apr 1 | Apr 3 | Apr 6 | Apr 9 | Apr 13 | Apr 17 |
| Low | 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 |
Freeze probabilities 1991–2020 at Grand Forks Univ (NWS), ND, from NOAA NCEI U.S. Climate Normals. Where a temperature is reached in fewer than 99.5% of years, the dates describe only the years that reach it. Not a forecast.
Frost risk on any date in 58201 →Compare Grand Forks with another place →
Weather by month in Grand Forks
July is the warmest month at Grand Forks Univ (NWS), ND, averaging 80°F by day and 59°F at night; January is the coldest at 15°F and -1°F. A freezing night is all but certain in every month from October to April (a 90% chance or more). From June to August the chance of a 32°F night stays under 10% each month. In spring, May still brings one in 82% of years.
Warmth for growing adds up to 2,193 growing degree days a year (base 50°F), more than at 55% of the 33 North Dakota stations. 32% of them (709) have built up by the end of June, and July adds the most, 603. Precipitation totals 22.8 inches a year, most in June (4.1") and least in January (0.5"); May to September bring 71% of it.
| Month | High °F | Low °F | Precip. in | 32°F night | Nights ≤ 32°F | GDD 50°F |
|---|---|---|---|---|---|---|
| Jan | 15 | -1 | 0.5 | 100% | 31 | 0 |
| Feb | 20 | 3 | 0.6 | 100% | 28 | 0 |
| Mar | 34 | 17 | 0.9 | 100% | 28 | 2 |
| Apr | 52 | 31 | 1.2 | 100% | 17 | 33 |
| May | 67 | 44 | 3.0 | 82% | 4 | 213 |
| Jun | 76 | 55 | 4.1 | 0% | 0 | 462 |
| Jul | 80 | 59 | 3.6 | 0% | 0 | 603 |
| Aug | 79 | 57 | 3.0 | 0% | 0 | 553 |
| Sep | 70 | 47 | 2.4 | 48% | 1 | 278 |
| Oct | 53 | 35 | 2.0 | 100% | 13 | 49 |
| Nov | 35 | 20 | 0.8 | 100% | 27 | 1 |
| Dec | 21 | 6 | 0.7 | 100% | 31 | 0 |
Monthly normals 1991–2020 at Grand Forks Univ (NWS), ND (830 ft), NOAA NCEI. "32°F night": chance of at least one in the month. GDD: growing degree days, base 50°F.
Compared with the next station
The nearest other station, Crookston NW Exp Stn, MN, 21 miles east of Grand Forks, has a last frost 1 day later (May 11), a first frost 4 days earlier (September 27), a season 6 days shorter.
When it snows in Grand Forks, North Dakota
The first measurable snow (0.1 inch or more) in Grand Forks usually arrives around October 31, and the last of the season around April 12. Those are the middle dates across the winters of 1991–2020 at Grand Forks Univ (NWS), ND, 2.4 miles away: half of years saw snow earlier, half later. Every one of those winters saw snow. The last 32°F night of spring typically comes 28 days after the last snow.
Planting calendar for 58201
| When | What to do |
|---|---|
| March 1 – March 15 | Start peppers and aubergines indoorsThey need eight to ten weeks under lights before they can go out. |
| March 15 – March 29 | Start tomatoes indoorsSix to eight weeks gives a transplant big enough to set fruit early. |
| April 12 – April 26 | Sow peas, spinach, lettuce, radish outdoorsThese tolerate light frost and prefer to germinate in cool soil. |
| May 10 onward | Transplant tomatoes, peppers, basil, squash, cucumbersThe average last freeze has passed — still watch the actual forecast. |
| by July 9 | Sow the autumn crop of carrots, beets and brassicasThey need about twelve weeks to size up before growth stops. |
| by September 17 | Harvest tender crops, or be ready to cover themA first freeze two weeks early is well within normal variation. |
| October 1 onward | Plant garlic, mulch beds, lift tender bulbsGarlic wants a cold spell; bare soil loses structure over winter. |
The weeks before and after the 50% dates are general rules of thumb, not NOAA figures; a seed packet gives the timing for each variety.
Where these figures come from
ZIP 58201 is 2 miles from Grand Forks Univ (NWS), ND, which stands at 830 feet, the nearest NOAA station that publishes freeze probabilities for 1991–2020. 4 other ZIP codes share the station. The 2023 USDA Plant Hardiness Zone Map lists ZIP 58201 in zone 4a, the band where the coldest night of the year averaged -30 to -25°F (-34.4 to -31.7°C) over 1991–2020; a zone describes winter lows, not frost dates.
Frost dates across North Dakota →
Hardiness zone and temperature range: USDA Plant Hardiness Zone Map 2023 (USDA-ARS, Oregon State University), ZIP-code listing, unchanged. °C converted from °F by this site.
Thirty-year averages, not a forecast: check the forecast before planting out. How stations are matched and which pages are offered to search engines: methodology.