Median last frost from May 6 to May 21 across North Dakota
NOAA stations
121
Median last frost, Minot
May 10
Passed in 9 of 10 years
May 22
Last frost
Last spring frost dates in North Dakota
Fargo and Minot in the Red River and Souris valleys reach a median last frost around May 10, Bismarck around May 14, and Williston on the Missouri around May 21.
Three dates per station from the NOAA 1991 to 2020 normals. The median is the date half of springs run past. The last column is the date the last 32°F night has passed by in 9 years out of 10, the one to hold tender transplants for.
Counted back from the median last frost at Minot, May 10. Pick another station to redraw the chart for it.
Start indoorsHarden offSet outSow outdoorsMedian last frostLast freeze passed in 9 of 10 years
Every crop, counted from a median last frost of May 10
Crop
Start indoors
Set out
Sow outdoors
Frost class
Tomato
Mar 22 to Apr 5
May 17 to May 24
Tender, very tender
Pepper
Mar 15 to Mar 29
May 24 to May 31
Tender, very tender
Eggplant
Mar 15 to Mar 29
May 24 to May 31
Tender, very tender
Basil
Mar 29 to Apr 12
May 24 to May 31
Tender
Celery
Feb 15 to Mar 1
May 10 to May 17
Tender
Cucumber
Apr 19 to Apr 26
May 17 to May 24
May 10 to May 17
Tender
Summer squash
Apr 26 to May 3
May 24 to May 31
May 10 to May 17
Tender
Winter squash
Apr 26 to May 3
May 24 to May 31
May 24 to May 31
Tender, very tender
Pumpkin
Apr 26 to May 3
May 24 to May 31
May 24 to May 31
Tender, very tender
Melon (cantaloupe)
Apr 26 to May 3
May 24 to May 31
Tender, very tender
Watermelon
Apr 19 to May 3
May 24 to May 31
Tender, very tender
Onion (from seed)
Feb 1 to Feb 15
Apr 12 to Apr 19
Hardy
Leek
Feb 1 to Feb 15
Apr 12 to Apr 19
Hardy
Parsley
Feb 8 to Feb 15
Apr 19 to Apr 26
Half-hardy
Broccoli
Mar 1 to Mar 15
Apr 12 to Apr 26
Hardy
Brussels sprouts
Mar 1 to Mar 15
Apr 12 to Apr 26
Hardy
Cabbage
Mar 1 to Mar 15
Apr 12 to Apr 19
Hardy
Cauliflower
Mar 15 to Mar 29
Apr 26 to May 3
Half-hardy
Kale
Mar 1 to Mar 15
Apr 12 to Apr 19
Hardy
Lettuce
Mar 8 to Mar 15
Apr 12 to Apr 19
Hardy
Swiss chard
Mar 15 to Mar 29
Apr 26 to May 3
Apr 12 to Apr 19
Half-hardy
Spinach
Feb 15 to Mar 1
Mar 29 to Apr 19
Apr 12 to Apr 26
Hardy
Peas
Apr 12 to Apr 26
Hardy
Radish
Apr 12 to Apr 26
Hardy
Carrot
Apr 26 to May 10
Half-hardy
Beet
Apr 26 to May 10
Half-hardy
Beans
May 10 to May 17
Tender
Sweet corn
May 10 to May 17
Tender
Tomato seedlings at the seed leaf stage, one to a pot. The University of Minnesota Extension holds off on fertilizer until a seedling has several sets of true leaves, then feeds at quarter strength once a week.“Tomato Seedlings (49768696597)” by Amanda Slater from Coventry, West Midlands, UK, CC BY-SA 2.0
Extension guide
What North Dakota State University advises
NDSU Extension (North Dakota State University) publishes the planting guide North Dakota gardeners work from, Field to Fork: Bell Peppers (FN2035).
“Bell peppers grow best when started from seeds indoors in late winter, followed by planting outside in late spring. Sow seeds indoors eight to 10 weeks before the date of your last spring frost.”
Setting out a tomato in June at a community garden. Tender crops go out after the last frost, and after a week or two of hardening off outdoors. “Volunteer planting heirloom tomato (4704185147)”, Pacific Southwest Region 5, Public domain
Seed starting questions for North Dakota
Count back from the median last frost where you garden. At Minot (Minot Intl Airport) that date is May 10, so for spring 2027 onions start indoors Feb 1 to Feb 15, peppers Mar 15 to Mar 29 and tomatoes Mar 22 to Apr 5. Across North Dakota's 121 NOAA stations the median last frost runs from May 6 to May 21 for the middle 90 percent, so a garden near Hettinger Municipal Airport starts later than one near Hillsboro 3 N.
It depends on the station. The earliest median last spring freeze in North Dakota is May 2 at Hillsboro 3 N; the latest is May 24 at Hettinger Municipal Airport. A median is a coin flip: at Minot the last 32°F freeze comes after May 10 in half of years, and has passed by May 22 in 9 of 10 years (NOAA 1991 to 2020 normals).
UNH Extension sets tomatoes out 1 to 2 weeks after the last frost, which at Minot is May 17 to May 24 in 2027. Tomatoes are frost tender, so the date to watch is May 22, when 9 of 10 springs at Minot have had their last 32°F night. Hardening off starts two weeks before setting out (May 3 to May 17).
NDSU Extension (North Dakota State University)'s Field to Fork: Bell Peppers puts it this way: "Bell peppers grow best when started from seeds indoors in late winter, followed by planting outside in late spring. Sow seeds indoors eight to 10 weeks before the date of your last spring frost." The guide is linked below with the date it was read (September 21, 2026).
UNH Extension gives 8 to 10 weeks from seed to transplant for both, and sets peppers out 2 weeks after the last frost and eggplant 2 to 3 weeks after, so the sowing date is 6 to 8 weeks before the median last frost. At Minot that is Mar 15 to Mar 29 for peppers.
About two weeks. University of Missouri Extension: "Hardening should be started about two weeks before planting in the garden." University of Minnesota Extension adds that seedlings should go out on a cloudy day or in the late afternoon.
Fargo and Minot in the Red River and Souris valleys reach a median last frost around May 10, Bismarck around May 14, and Williston on the Missouri around May 21. Each station carries its own dates: Fargo May 10 and Williston Sloulin Intl Airport May 21 at the median.
