Frost Dates for Grand Forks, ND 58201

Last spring frost May 10 · First fall frost September 27 · 140 frost-free days · USDA Zone 4a

Frost probability for 58201

Frost10%50%90%
Spring (last frost)May 22May 10April 24
Fall (first frost)September 17September 27October 7

Dates come from NOAA 1971–2000 freeze probabilities at the nearest reporting station (6.6 km away); the 50% date is the median year.

Frost dates by ZIP code in Grand Forks, ND

ZIPLast spring frost (50%)First fall frost (50%)Zone
58201May 10September 274a
58203May 12September 214a
58202May 11September 23Zone 5b

Month by month in Grand Forks

MonthWhat to do
JanuaryPlan your garden layout and order seeds. Research varieties suited to your frost dates.
FebruaryStart the slowest-growing crops indoors: onions, leeks, and celery (10–12 weeks before last frost).
MarchStart peppers and eggplant indoors 8–10 weeks before your last frost (around May 10). Start tomatoes about two weeks later, 6–8 weeks before last frost.
AprilStart herbs, basil, and squash indoors (4–6 weeks before frost). Direct sow peas, spinach, and lettuce if soil is workable.
MayLast frost around May 10. Transplant cold-hardy crops (broccoli, kale, cabbage). Harden off tomato and pepper seedlings.
JuneFrost has passed. Transplant tomatoes, peppers, and basil outdoors. Direct sow beans, cucumbers, squash, and zucchini.
JulySuccession plant lettuce and greens. Keep beds weeded and watered consistently.
AugustFirst fall frost approaching (around September 27). Transplant fall brassicas. Sow spinach, arugula, and radishes.
SeptemberFirst frost around September 27. Harvest tomatoes and peppers before frost. Cover cold-hardy crops with row covers to extend the season.
OctoberHarvest remaining cold-hardy crops: kale, carrots, and beets. Plant garlic bulbs for next year.
NovemberClean up spent plants. Add compost to beds. Rest, review, and plan next year's garden.
DecemberClean up spent plants. Add compost to beds. Rest, review, and plan next year's garden.

What grows in a 140-day season

Frequently Asked Questions

What is the last frost date for Grand Forks, ND (ZIP 58201)?

The median last spring frost date for Grand Forks, ND (ZIP code 58201) is around May 10. This is the 50th-percentile date — meaning half of all years see frost end before this date. Use the 10% and 90% dates to understand the full range of risk in your area.

What is the first fall frost date in Grand Forks, ND?

The median first fall frost date for Grand Forks, ND is around September 27. Plan to harvest or protect frost-sensitive crops like tomatoes and peppers at least a week before this date to avoid losses.

How long is the growing season in Grand Forks, ND?

The frost-free growing season in Grand Forks is about 140 days. This window — from your last spring frost to your first fall frost — is when warm-season vegetables thrive. Cold-hardy crops like kale, spinach, and peas can extend your season by weeks on either side.

What USDA hardiness zone is Grand Forks, ND?

Based on frost date patterns, Grand Forks falls approximately in 4a. USDA hardiness zones are determined by average annual minimum winter temperatures and guide both plant selection and planting timing for your location.

When should I start tomatoes indoors in Grand Forks, ND?

Start tomato seeds indoors 6–8 weeks before your last frost date (around May 10). For Grand Forks, that's roughly March 15 to March 29. Transplant outdoors 1–2 weeks after your last frost.

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