Harmon County climate

Harmon County Frost Dates and Growing Season

NOAA 1991-2020 normals for Hollis 5E, 7.6 km from Harmon County, elevation 1621 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hollis 5E. 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 10 and the first fall freeze around October 28, a growing season of about 200 days.

Median at 36°F
last April 20, first October 21
Median at 32°F
last April 10, first October 28
Median at 28°F
last March 31, first November 6

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 26Apr 23Apr 20Apr 18Apr 15Apr 12Apr 7
32°FApr 24Apr 19Apr 16Apr 13Apr 10Apr 7Apr 4Apr 1Mar 27
28°FApr 14Apr 8Apr 5Apr 2Mar 31Mar 27Mar 24Mar 19Mar 13
24°FApr 4Mar 31Mar 26Mar 22Mar 19Mar 15Mar 11Mar 6Feb 28
20°FMar 25Mar 19Mar 14Mar 10Mar 6Mar 3Feb 28Feb 24Feb 16
16°FMar 15Mar 8Mar 4Feb 28Feb 25Feb 20Feb 14Feb 7Jan 30

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 12Oct 16Oct 18Oct 21Oct 23Oct 25Oct 27Oct 31
32°FOct 15Oct 20Oct 23Oct 26Oct 28Oct 31Nov 2Nov 5Nov 11
28°FOct 22Oct 27Oct 31Nov 3Nov 6Nov 9Nov 12Nov 16Nov 21
24°FOct 30Nov 5Nov 8Nov 12Nov 15Nov 19Nov 23Nov 27Dec 2
20°FNov 7Nov 14Nov 19Nov 23Nov 26Nov 30Dec 3Dec 7Dec 14
16°FNov 18Nov 24Nov 29Dec 4Dec 8Dec 13Dec 17Dec 23Jan 1

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°F198193189185181179175170164
32°F219212208204200196192188182
28°F241233228223219215211205197
24°F264256250245240235230224217
20°F290282274269264259253247237
16°F320308302295290284277271261

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
3,712
Cooling degree days, base 65°F
2,056
Growing degree days, base 40°F
7,879
Growing degree days, base 45°F
6,409
Growing degree days, base 50°F
5,099
Growing degree days, base 55°F
3,938
Growing degree days, base 60°F
2,926

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January83909
February657024
March4705121
April21233292
May52172585
June1420868
July05601,025
August0529993
September16283717
October17352361
November496291
December797013

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 7.6 km from Harmon 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 USC00344249 (Hollis 5E). Public domain.