Frost dates · USDA zone 4a
Frost dates for Grand Forks, ND
Grand Forks, ND sees its last 32 °F night of spring around May 10 and its first of fall around October 1 — a 144-day freeze-free season in a typical year.
Pick a sauce; the Plan Builder runs this station's dates and hands back the calendar, plant count and gear list.
Freeze odds, by date
| Odds | Last spring freeze after | First fall freeze before |
|---|---|---|
| 9 years in 10 | Apr 28 | Oct 15 |
| Median — 1 year in 2 | May 10 | Oct 1 |
| 1 year in 10 | May 24 | Sep 20 |
The top row is the risky edge: in 9 years of 10 a spring freeze still comes after it, so tender transplants set out then need cover. The bottom row is the cautious date — only 1 year in 10 freezes after it — and the one to plan uncovered tender transplants against. Freeze-free season: 144 days median, at least 126 in 9 years of 10, at least 161 days in 1 year of 10. NOAA ranks season length year by year, so it is not the gap between two rows above. A hard freeze (28 °F) has a median last date of Apr 30 and first of Oct 12.
Grand Forks planting calendar, 2027
Every row runs from the median last frost (May 10) and median first frost (Oct 1) above, using each cultivar's days to maturity. Same engine as the Plan Builder.
| Crop | Start indoors | Transplant / plant | First harvest | Days |
|---|---|---|---|---|
| Hardneck GarlicSiberian (porcelain hardneck) | — | Oct 15prior fall | Jun 12 | 240 from sow |
| Spanish OnionYellow Sweet Spanish (long-day) | Feb 15 | Apr 12 | Jul 31 | 110 from transplant |
| Mustard greensGarnet Giant (Brassica juncea) | Direct sow | May 10 | Jun 9 | 30 from sow |
| CilantroSlow Bolt (Coriandrum sativum) | Apr 26 | Apr 26 | Jun 10 | 45 from sow |
| Genovese BasilGenovese | Apr 12 | May 24 | Jul 23 | 60 from transplant |
| CayenneLong Slim Cayenne (Capsicum annuum) | Mar 15 | May 17 | Jul 31 | 75 from transplant |
| HabaneroOrange Habanero (Capsicum chinense) | Mar 1 | May 24 | Aug 27 | 95 from transplant |
| JalapeñoEarly Jalapeño (Capsicum annuum) | Mar 15 | May 17 | Jul 31 | 75 from transplant |
| Marconi Red PepperMarconi Red (Capsicum annuum) | Mar 15 | May 17 | Aug 5 | 80 from transplant |
| SerranoSerrano Tampiqueño (Capsicum annuum) | Mar 15 | May 17 | Aug 5 | 80 from transplant |
| Nantes CarrotScarlet Nantes | Apr 26 | Apr 26 | Jul 5 | 70 from sow |
| TomatilloToma Verde | Mar 29 | May 17 | Jul 26 | 70 from transplant |
| Roma TomatoRoma VF (determinate paste) | Mar 29 | May 17 | Jul 31 | 75 from transplant |
| San Marzano TomatoSan Marzano (indeterminate paste) | Mar 29 | May 17 | Aug 5 | 80 from transplant |
Tight means first harvest lands within two weeks of the median first fall frost: start that crop indoors on time or cover it in fall.
What sauce can Grand Forks grow?
Each sauce, scheduled for a Grand Forks container garden: when the first seeds go in and when enough fruit has ripened for one batch.
Grand Forks frost questions
When is the last frost in Grand Forks, ND?
The median last 32 °F freeze at GRAND FORKS UNIV (NWS), ND is May 10: half of years see a later one. One year in ten, a freeze still comes after May 24; nine years in ten, it comes after April 28. Source: NOAA NCEI 1991–2020 U.S. Climate Normals.
When is the first frost in Grand Forks, ND?
The median first 32 °F freeze of fall is October 1. One year in ten it arrives before September 20; nine years in ten, before October 15.
How long is the growing season in Grand Forks, ND?
144 days between the last spring and first fall 32 °F freeze in a median year. Nine years in ten the season runs at least 126 days; one year in ten, at least 161 days.
What growing zone is Grand Forks, ND?
USDA hardiness zone 4a, per the 2023 USDA Plant Hardiness Zone Map for ZIP 58201. A zone describes the coldest winter night, not when frost ends, so it is the wrong number for a planting calendar — the frost dates on this page are the right one.
When should I plant tomatoes in Grand Forks, ND?
Start Roma VF (determinate paste) seeds indoors around Mar 29 and transplant around May 17, 1 week after the median last frost. To cut the freeze risk to one year in ten, wait for May 24. First ripe fruit lands around Jul 31.
When should I plant peppers in Grand Forks, ND?
Sow jalapeño indoors on a heat mat around Mar 15; transplant no earlier than May 17, and wait past it until nights hold above 50 °F — that can run weeks later. First green pods around Jul 31.
Nearby in North Dakota
- Fargolast frost May 5
- West Fargolast frost May 10
- Bismarcklast frost May 10
- Minotlast frost May 10
All North Dakota frost dates → · How frost-date math drives a sowing calendar →