Clay County climate

Clay County Frost Dates and Growing Season

NOAA 1991-2020 normals for Moorhead, 19.6 km from Clay County, elevation 904 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Moorhead. 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 5 and the first fall freeze around October 3, a growing season of about 150 days.

Median at 36°F
last May 15, first September 24
Median at 32°F
last May 5, first October 3
Median at 28°F
last April 28, first October 14

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°FMay 29May 24May 21May 18May 15May 13May 10May 7May 3
32°FMay 20May 14May 11May 8May 5May 3May 1Apr 28Apr 23
28°FMay 9May 5May 2Apr 30Apr 28Apr 24Apr 21Apr 18Apr 12
24°FMay 1Apr 28Apr 24Apr 20Apr 17Apr 14Apr 12Apr 8Apr 4
20°FApr 23Apr 18Apr 15Apr 12Apr 9Apr 6Apr 4Apr 1Mar 28
16°FApr 17Apr 12Apr 8Apr 5Apr 3Apr 1Mar 29Mar 25Mar 18

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 12Sep 17Sep 20Sep 22Sep 24Sep 26Sep 28Oct 1Oct 5
32°FSep 22Sep 25Sep 28Oct 1Oct 3Oct 6Oct 9Oct 13Oct 18
28°FOct 1Oct 4Oct 8Oct 11Oct 14Oct 18Oct 21Oct 24Oct 29
24°FOct 9Oct 14Oct 18Oct 21Oct 25Oct 28Oct 31Nov 3Nov 7
20°FOct 18Oct 24Oct 28Oct 31Nov 2Nov 4Nov 6Nov 10Nov 14
16°FOct 27Nov 1Nov 4Nov 6Nov 9Nov 11Nov 14Nov 18Nov 23

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°F148141138134131128124119113
32°F169162157154150146142138132
28°F189182177173169165160155149
24°F209201196192188184179173167
20°F223217212208203199195191184
16°F241233226222218214210206199

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
8,822
Cooling degree days, base 65°F
566
Growing degree days, base 40°F
4,272
Growing degree days, base 45°F
3,308
Growing degree days, base 50°F
2,453
Growing degree days, base 55°F
1,704
Growing degree days, base 60°F
1,070

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,75300
February1,44900
March1,17304
April662142
May28027251
June56119513
July13207659
August25164604
September19646315
October612363
November1,06701
December1,53800

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 19.6 km from Clay County. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00215586 (Moorhead). Public domain.