USDA hardiness zone lookup
Grand Forks, ND — USDA Zone 3b
Grand Forks, North Dakota · 128-day growing season
Frost dates and growing season in Grand Forks
| USDA hardiness zone | Zone 3b |
|---|---|
| Average last spring frost | May 16 |
| Average first fall frost | September 21 |
| Growing season length | ~128 days |
| Temperature range (F) | -30 to -20°F |
| Temperature range (C) | -34 to -29°C |
All of Grand Forks's mapped ZIP codes fall in the same hardiness band, Zone 3b.
These are 50%-probability averages modeled from Grand Forks's USDA hardiness zone and regional climate normals — not a single-station reading. In a typical year the last spring frost will have passed by May 16, but a colder-than-average year can run 1-2 weeks later. Plant tender crops (tomatoes, peppers, basil) once both soil and night temperatures are consistently warm — a thermometer beats the calendar.
Growing season in Grand Forks
Grand Forks, North Dakota sits in USDA Zone 3b, with roughly 128 frost-free days between an average last spring frost around May 16 and a first fall frost around September 21. That is a standard temperate season — most common vegetables finish comfortably, and a single main planting plus one succession round works well.
What grows in Grand Forks
Grand Forks falls in USDA Zone 3b, so the same hardiness constraints apply as the full Zone 4 guide. Vegetables, herbs, and fruit trees rated to Zone 3b (or hardier) will overwinter here in a typical year.
- Apple, pear, plum, sour cherry
- Blueberries (highbush)
- Raspberries
- Strawberries
- Tomatoes
- Peppers (short-season)
- Cucumbers
- Beans
- Squash (summer + winter)
- Garlic
What to plant in Grand Forks this week
Grand Forks's last frost is around May 16. This is the spring transplant window — start tomatoes and peppers indoors if you haven't, and direct-sow cold-tolerant crops now.
- When to plant tomatoes in zone 4
- When to plant peppers in zone 4
- When to plant basil in zone 4
- When to plant bush beans in zone 4
- When to plant cucumbers in zone 4
Full planting calendar for Grand Forks
Crop-by-crop sowing, transplant, and harvest dates calibrated to zone 4 averages:
- When to plant tomatoes in zone 4
- When to plant peppers in zone 4
- When to plant basil in zone 4
- When to plant garlic in zone 4
- When to plant lettuce in zone 4
- When to plant bush beans in zone 4
- When to plant cucumbers in zone 4
- When to plant summer squash in zone 4
- When to plant peas in zone 4
- When to plant carrots in zone 4
ZIP codes in Grand Forks
Drill down to the precise frost window and planting calendar for a specific ZIP in Grand Forks:
Local microclimate notes
Zone tables give you the average — but Grand Forksgardens vary. South-facing walls and paved areas can run a full half-zone warmer than the published rating. Low-lying spots, frost pockets, and shaded north sides can run colder. If you've gardened here a few seasons, your own frost record — the last time you actually got frost damage — beats any national average.
Source and methodology
Hardiness zone from the USDA Plant Hardiness Zone Map (2023 revision). Frost-date and growing-season figures are modeled from Grand Forks's USDA hardiness zone and regional NOAA 1991-2020 climate normals — zone-level estimates, not a per-station record, so treat them as planning guidance and confirm against your own local frost history. Crop recommendations draw on US Cooperative Extension references, curated by the Growli editorial team. Last reviewed June 2026.
Other cities in North Dakota
- Bismarck, ND — USDA Zone 4a
- Fargo, ND — USDA Zone 4a
- Minot, ND — USDA Zone 4a
- All of North Dakota by zone