Frost dates for Grand Forks, North Dakota
In Grand Forks, half of springs have had their last frost by May 16 (and 1 spring in 10 still has one after May 31), and half of falls have had their first frost by September 27, leaving about 133 frost-free days in a typical year. Here is how sure those dates are, what they mean for planting, and where they come from.
Frost dates for
Grand Forks, North Dakota
Last spring frost
May 16
Half of springs have their last frost by this date. For a safer bet, wait until May 31: only 1 spring in 10 has a frost after that.
First fall frost
September 27
Half of falls have their first frost by this date. In 1 fall in 10 it comes by September 15.
Growing season
133 days
Frost-free days in a typical year. 9 years in 10 get at least 114.
Hardiness zone
Not listed
This ZIP code isn't in the USDA's ZIP code list for the 2023 map.
Print a year planner for Grand Forks
Frost risk through the year
How sure are these dates?
A frost date is a probability, not a promise. NOAA worked out, from 30 years of nightly lows, how often the last spring frost and the first fall frost fall on each date. The middle column is the typical year. The outer columns are the early and late years that come about once a decade.
| Early year 1 in 10 | Typical year 1 in 2 | Late year 1 in 10 | |
|---|---|---|---|
| Last frost in spring | May 3 | May 16 | May 31 |
| First frost in fall | September 15 | September 27 | October 8 |
The frost-free season between them runs 133 days in a typical year. In 1 year in 10 it is 150 days or longer, and in 1 year in 10 it is 114 days or shorter.
- Hard freeze (28°F): typically last on May 4 and first on October 5. It is a harder freeze than the 32°F frost line, cold enough to damage many garden plants; how hardy a crop is decides whether it comes through. (The National Weather Service's own hard-freeze threshold varies from office to office.)
- Frost possible (36°F at the station): typically last on May 26 and first on September 18. On clear, still nights the ground can be several degrees colder than the thermometer, so frost can form on plants when the official reading is in the mid-30s.
In 8 springs out of 10, the last frost in Grand Forks comes between May 3 and May 31, a window of 28 days. That is about average for NOAA's stations (the typical window is 31 days).
Among North Dakota's 125 NOAA stations with a frost every year, 30 percent have their typical last frost later than Grand Forks does.
Planting calendar for Grand Forks
These dates count from the typical last and first frosts, using the planting rules published by Colorado State University Extension (spring), Virginia Cooperative Extension (fall crops) and University of Minnesota Extension (garlic, where winters are hard). Weather in any one year can run early or late, so check the forecast before you plant tender crops.
Your season is too short for a separate fall planting of cabbage and broccoli: sown late enough to be a fall crop, it wouldn't be ready before the typical first frost. Your spring planting is your harvest.
| When | What to do | Why then |
|---|---|---|
| February | ||
| February 28 to March 28 | Broccoli and cabbage Start seeds indoors | 5 to 7 weeks before planting them out |
| March | ||
| March 14 to April 11 | Cauliflower Start seeds indoors | 5 to 7 weeks before planting out |
| March 28 to April 18 | Eggplant Start seeds indoors | 6 to 9 weeks before planting out |
| April | ||
| April 4 to 18 | Peppers Start seeds indoors | 6 to 8 weeks before planting out |
| April 11 to 25 | Tomatoes Start seeds indoors | 5 to 7 weeks before planting out |
| April 18 to May 2 | Peas, spinach, lettuce, radishes, onion sets, turnips Sow outdoors, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| April 18 to May 2 | Broccoli and cabbage Plant out, as early as | hardy crops: 2 to 4 weeks before the typical last frost |
| May | ||
| May 2 to 16 | Beets, carrots, potatoes, Swiss chard Plant outdoors, as early as | semi-hardy crops: up to 2 weeks before the typical last frost |
| May 2 to 16 | Cauliflower Plant out, as early as | semi-hardy: up to 2 weeks before the typical last frost |
| May 16 | Snap beans, sweet corn, cucumbers, summer squash Sow outdoors around | tender crops: around the typical last frost date |
| May 30 | Tomatoes, peppers, eggplant Plant out from | very tender: 2 weeks or more after the typical last frost |
| May 30 | Melons, winter squash, pumpkins, lima beans Sow outdoors from | very tender: 2 weeks or more after the typical last frost |
| July | ||
| July 1 | Snap beans for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| July 5 | Carrots for fall Last date to sow | 70 days to harvest, plus 2 weeks for slower fall growth |
| July 6 | Cucumbers for fall Last date to sow | 55 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| July 10 | Peas for fall Last date to sow | 65 days to harvest, plus 2 weeks for slower fall growth |
| July 11 | Summer squash for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth, plus 2 weeks because frost kills it |
| July 15 | Leaf lettuce and beets for fall Last date to sow | 60 days to harvest, plus 2 weeks for slower fall growth |
| July 25 | Turnips and kohlrabi for fall Last date to sow | 50 days to harvest, plus 2 weeks for slower fall growth |
| August | ||
| August 4 | Spinach for fall Last date to sow | 40 days to harvest, plus 2 weeks for slower fall growth |
| August 14 | Radishes for fall Last date to sow | 30 days to harvest, plus 2 weeks for slower fall growth |
| September | ||
| September 15 | Tomatoes, peppers, squash, melons, cucumbers Watch the forecast from | in 1 fall in 10 the first frost comes by this date; pick tender crops before a frost |
| October | ||
| October 12 to 19 | Garlic Plant cloves | one or two weeks after the typical first hard freeze (28°F), our reading of the first killing frost |
Want more insurance? Shift every spring date 15 days later. That plans around May 31, the date after which only 1 spring in 10 has a frost.
For spring bulbs such as tulips and daffodils, plant once the soil has cooled to about 50 to 55°F and keep going until a couple of weeks before the ground freezes. Our guide to fall planting explains how to tell.
Where these numbers come from
These dates come from NOAA's weather station Grand Forks International Airport (station USW00014916), 5 miles from the center of Grand Forks. It sits at about the same elevation, 840 feet above sea level. NOAA rates this station's record as standard: at least 24 of the 30 years, with gaps filled from nearby stations.
Our ZIP code lookup matches these 7 ZIP codes to the same station, so they get the same dates: 58203, 58204, 58205, 58228, 58235, 58256, 58258. Hardiness zones are worked out separately for each ZIP code.
The nearest other places with pages
- Fargo, North Dakota: last frost around May 10, first frost around September 30 (75 miles away)
See frost dates across North Dakota, or look up your own ZIP code for the station nearest you. Want the background? Read what a last frost date really means.