Grand Forks County climate

Grand Forks County Frost Dates and Growing Season

NOAA 1991-2020 normals for Grand Forks Intl AP, 20.5 km from Grand Forks County, elevation 842 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Grand Forks Intl AP. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

The last spring freeze typically comes around May 16 and the first fall freeze around September 27, a growing season of about 133 days.

Median at 36°F
last May 26, first September 18
Median at 32°F
last May 16, first September 27
Median at 28°F
last May 4, first October 5

Last freeze in spring

The chance of a later freeze than the date shown. At 10 percent, one spring in ten still freezes after the date; planting after the 10 percent date for 32°F is the cautious choice.

Threshold10%20%30%40%50%60%70%80%90%
36°FJun 7Jun 3Jun 1May 29May 26May 23May 20May 17May 13
32°FMay 31May 26May 21May 18May 16May 13May 10May 7May 3
28°FMay 19May 14May 10May 7May 4May 1Apr 29Apr 26Apr 20
24°FMay 9May 3Apr 30Apr 28Apr 24Apr 21Apr 17Apr 13Apr 7
20°FApr 29Apr 24Apr 20Apr 16Apr 13Apr 10Apr 7Apr 4Mar 31
16°FApr 19Apr 15Apr 11Apr 8Apr 5Apr 3Apr 1Mar 28Mar 20

First freeze in fall

The chance of an earlier freeze than the date shown. At 10 percent, one fall in ten freezes before the date.

Threshold10%20%30%40%50%60%70%80%90%
36°FSep 4Sep 9Sep 12Sep 15Sep 18Sep 20Sep 22Sep 25Sep 28
32°FSep 15Sep 19Sep 22Sep 24Sep 27Sep 29Oct 1Oct 3Oct 8
28°FSep 23Sep 28Oct 1Oct 2Oct 5Oct 7Oct 10Oct 14Oct 19
24°FOct 2Oct 5Oct 8Oct 12Oct 15Oct 18Oct 21Oct 25Oct 29
20°FOct 10Oct 15Oct 19Oct 22Oct 26Oct 29Nov 1Nov 3Nov 7
16°FOct 18Oct 24Oct 29Oct 31Nov 2Nov 5Nov 8Nov 11Nov 15

Growing season length

Days between the last spring and first fall freeze at each threshold, with the chance of a season at least that long.

Threshold10%20%30%40%50%60%70%80%90%
36°F13212512011711310910510296
32°F150146141137133129125121114
28°F171164160156152149145140135
24°F194187181177172168164159152
20°F215208203198193189185178171
16°F229223217214210207202198191

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
100% of years
32°F or colder
100% of years
28°F or colder
100% of years
24°F or colder
100% of years
20°F or colder
100% of years
16°F or colder
100% of years

Degree days

A degree day is one degree of the daily mean temperature beyond a base, for one day. Heating degree days count cold (the fuel a house burns), cooling degree days heat, growing degree days the warmth a crop needs; each crop has its own base.

Heating degree days, base 65°F
9,533
Cooling degree days, base 65°F
384
Growing degree days, base 40°F
3,791
Growing degree days, base 45°F
2,880
Growing degree days, base 50°F
2,076
Growing degree days, base 55°F
1,384
Growing degree days, base 60°F
812

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,81800
February1,52300
March1,25702
April731024
May35215190
June9079441
July27147584
August49112529
September24429261
October678244
November1,14801
December1,61800

What this means

NOAA computes these from the daily lows at the station over 1991-2020, fitting the dates of each year's last and first freeze to a distribution, so a date can be stated at any level of risk. 36°F is a frost risk for tender plants on a clear, calm night, since the ground cools below the air above it; 32°F is a freeze; 28°F is a hard freeze that kills most annuals.

The station is 20.5 km from Grand Forks County. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USW00014916 (Grand Forks Intl AP). Public domain.