Harlan County climate

Harlan County Frost Dates and Growing Season

NOAA 1991-2020 normals for Ragan, 17.9 km from Harlan County, elevation 2240 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ragan. 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 24 and the first fall freeze around October 18, a growing season of about 174 days.

Median at 36°F
last May 3, first October 9
Median at 32°F
last April 24, first October 18
Median at 28°F
last April 12, first October 27

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 15May 10May 7May 5May 3Apr 30Apr 28Apr 24Apr 20
32°FMay 7May 2Apr 30Apr 27Apr 24Apr 20Apr 17Apr 13Apr 8
28°FApr 29Apr 23Apr 19Apr 15Apr 12Apr 8Apr 5Apr 2Mar 28
24°FApr 17Apr 11Apr 7Apr 4Apr 2Mar 31Mar 26Mar 23Mar 16
20°FApr 8Apr 3Mar 31Mar 28Mar 24Mar 21Mar 17Mar 12Mar 6
16°FApr 1Mar 26Mar 22Mar 17Mar 13Mar 9Mar 5Mar 1Feb 24

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

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°F173168163160156153149144138
32°F194187183178174170166162154
28°F215209204200196192187181175
24°F235227222219215211206201195
20°F254246241236231227222216210
16°F276268261255251246240232224

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
5,902
Cooling degree days, base 65°F
1,081
Growing degree days, base 40°F
5,693
Growing degree days, base 45°F
4,498
Growing degree days, base 50°F
3,441
Growing degree days, base 55°F
2,519
Growing degree days, base 60°F
1,731

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,18900
February96203
March754037
April4366131
May18152347
June24229656
July3365827
August6297756
September89119485
October38913173
November758026
December1,11300

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 17.9 km from Harlan 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 USC00257002 (Ragan). Public domain.