Griggs County climate

Griggs County Frost Dates and Growing Season

NOAA 1991-2020 normals for Cooperstown, 16 km from Griggs County, elevation 1380 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Cooperstown. 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 17 and the first fall freeze around September 23, a growing season of about 128 days.

Median at 36°F
last May 27, first September 14
Median at 32°F
last May 17, first September 23
Median at 28°F
last May 7, first October 2

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 10Jun 4Jun 1May 29May 27May 24May 20May 17May 14
32°FJun 1May 27May 24May 21May 17May 15May 12May 9May 5
28°FMay 22May 16May 13May 10May 7May 4May 1Apr 29Apr 23
24°FMay 12May 6May 2Apr 29Apr 26Apr 23Apr 19Apr 14Apr 10
20°FMay 2Apr 27Apr 23Apr 19Apr 15Apr 13Apr 10Apr 7Apr 3
16°FApr 23Apr 17Apr 14Apr 10Apr 8Apr 5Apr 3Mar 31Mar 25

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°FAug 29Sep 3Sep 8Sep 11Sep 14Sep 16Sep 18Sep 21Sep 25
32°FSep 10Sep 15Sep 18Sep 21Sep 23Sep 25Sep 28Oct 1Oct 5
28°FSep 19Sep 24Sep 27Sep 30Oct 2Oct 5Oct 7Oct 10Oct 15
24°FSep 29Oct 2Oct 5Oct 9Oct 11Oct 15Oct 18Oct 21Oct 25
20°FOct 6Oct 11Oct 15Oct 18Oct 21Oct 24Oct 28Oct 31Nov 4
16°FOct 15Oct 20Oct 24Oct 27Oct 30Nov 1Nov 4Nov 7Nov 11

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°F1281221171131091041009485
32°F147140136132128124120115109
28°F167160155151147143139135128
24°F188181176171167163158152145
20°F206199195191186183178173165
16°F223216212206203198195190183

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
9,619
Cooling degree days, base 65°F
307
Growing degree days, base 40°F
3,631
Growing degree days, base 45°F
2,724
Growing degree days, base 50°F
1,929
Growing degree days, base 55°F
1,248
Growing degree days, base 60°F
699

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,80900
February1,51700
March1,25702
April736125
May36412178
June10662408
July37118546
August6590490
September26224238
October691141
November1,16101
December1,61300

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 16 km from Griggs 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 USC00321766 (Cooperstown). Public domain.