Clay County climate

Clay County Frost Dates and Growing Season

NOAA 1991-2020 normals for Henrietta, 3.1 km from Clay County, elevation 930 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Henrietta. 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 April 1 and the first fall freeze around November 8, a growing season of about 221 days.

Median at 36°F
last April 9, first November 1
Median at 32°F
last April 1, first November 8
Median at 28°F
last March 20, first November 18

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°FApr 24Apr 19Apr 16Apr 13Apr 9Apr 6Apr 3Mar 31Mar 27
32°FApr 17Apr 10Apr 7Apr 4Apr 1Mar 29Mar 24Mar 20Mar 13
28°FApr 8Apr 1Mar 27Mar 23Mar 20Mar 16Mar 11Mar 5Feb 28
24°FMar 25Mar 19Mar 14Mar 10Mar 6Mar 2Feb 27Feb 23Feb 15
20°FMar 12Mar 6Mar 2Feb 27Feb 22Feb 16Feb 9Feb 3Jan 24
16°FMar 3Feb 26Feb 17Feb 9Feb 5Jan 31Jan 24Jan 15Dec 31

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°FOct 16Oct 21Oct 24Oct 28Nov 1Nov 3Nov 5Nov 9Nov 14
32°FOct 23Oct 29Nov 1Nov 5Nov 8Nov 12Nov 15Nov 20Nov 29
28°FNov 1Nov 6Nov 11Nov 14Nov 18Nov 22Nov 27Dec 1Dec 7
24°FNov 10Nov 16Nov 21Nov 26Nov 30Dec 4Dec 8Dec 13Dec 22
20°FNov 19Nov 27Dec 1Dec 7Dec 12Dec 19Dec 26Jan 2Jan 12
16°FDec 1Dec 9Dec 17Dec 24Dec 31Jan 6Jan 14Jan 23Feb 4

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°F225217212207203199195191182
32°F249239232226221217212206198
28°F272262255249244238232225214
24°F299288281274268262255249240
20°F333318310304297292283276264
16°F365362347334328320310304292

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
90% 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
2,998
Cooling degree days, base 65°F
2,290
Growing degree days, base 40°F
8,651
Growing degree days, base 45°F
7,080
Growing degree days, base 50°F
5,657
Growing degree days, base 55°F
4,380
Growing degree days, base 60°F
3,258

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January718028
February559252
March35717200
April15858362
May26210649
June1424873
July05861,050
August05551,019
September12321759
October115104464
November39313157
December661143

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 3.1 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 USC00414093 (Henrietta). Public domain.