Harper County climate

Harper County Frost Dates and Growing Season

NOAA 1991-2020 normals for Anthony, 5.8 km from Harper County, elevation 1340 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Anthony. 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 9 and the first fall freeze around October 30, a growing season of about 205 days.

Median at 36°F
last April 20, first October 22
Median at 32°F
last April 9, first October 30
Median at 28°F
last March 31, first November 7

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 2Apr 29Apr 25Apr 22Apr 20Apr 17Apr 13Apr 10Apr 4
32°FApr 23Apr 19Apr 15Apr 12Apr 9Apr 6Apr 3Mar 31Mar 26
28°FApr 15Apr 10Apr 6Apr 3Mar 31Mar 27Mar 22Mar 17Mar 11
24°FApr 5Mar 31Mar 26Mar 21Mar 17Mar 13Mar 9Mar 5Mar 1
20°FMar 25Mar 17Mar 12Mar 8Mar 5Mar 2Feb 28Feb 24Feb 17
16°FMar 14Mar 8Mar 4Mar 1Feb 26Feb 22Feb 17Feb 12Feb 2

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 7Oct 14Oct 17Oct 20Oct 22Oct 24Oct 27Oct 30Nov 4
32°FOct 17Oct 22Oct 25Oct 27Oct 30Nov 1Nov 4Nov 8Nov 12
28°FOct 25Oct 29Nov 1Nov 5Nov 7Nov 11Nov 14Nov 18Nov 23
24°FOct 31Nov 5Nov 10Nov 13Nov 16Nov 19Nov 23Nov 28Dec 2
20°FNov 7Nov 14Nov 19Nov 23Nov 26Nov 30Dec 3Dec 7Dec 13
16°FNov 17Nov 23Nov 28Dec 3Dec 8Dec 12Dec 17Dec 23Dec 30

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°F203197193188185181177172167
32°F224218212208205200196191185
28°F244236232227223218214209202
24°F268260253248244239234227219
20°F291282275271265260255247239
16°F314304297291286281274268259

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
4,436
Cooling degree days, base 65°F
1,715
Growing degree days, base 40°F
7,118
Growing degree days, base 45°F
5,752
Growing degree days, base 50°F
4,533
Growing degree days, base 55°F
3,458
Growing degree days, base 60°F
2,522

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January97503
February773016
March567383
April28917222
May82124509
June3349796
July0509973
August0448913
September28225647
October23240302
November576164
December91105

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 5.8 km from Harper 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 USW00013980 (Anthony). Public domain.