Grayson County climate

Grayson County Frost Dates and Growing Season

NOAA 1991-2020 normals for Leitchfield 2 N, 7.4 km from Grayson County, elevation 620 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Leitchfield 2 N. 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 26 and the first fall freeze around October 15, a growing season of about 172 days.

Median at 36°F
last May 4, first October 6
Median at 32°F
last April 26, first October 15
Median at 28°F
last April 14, first October 24

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 19May 14May 10May 7May 4May 1Apr 29Apr 25Apr 21
32°FMay 11May 5May 2Apr 29Apr 26Apr 22Apr 18Apr 15Apr 11
28°FApr 30Apr 24Apr 19Apr 16Apr 14Apr 11Apr 9Apr 5Mar 30
24°FApr 17Apr 12Apr 9Apr 6Apr 2Mar 31Mar 29Mar 24Mar 19
20°FApr 8Apr 3Mar 31Mar 28Mar 24Mar 20Mar 17Mar 11Mar 4
16°FMar 29Mar 23Mar 19Mar 16Mar 11Mar 6Mar 2Feb 27Feb 21

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 25Sep 30Oct 2Oct 4Oct 6Oct 8Oct 10Oct 13Oct 17
32°FOct 4Oct 7Oct 10Oct 12Oct 15Oct 17Oct 20Oct 22Oct 26
28°FOct 11Oct 16Oct 19Oct 22Oct 24Oct 27Oct 30Nov 1Nov 5
24°FOct 21Oct 25Oct 30Nov 1Nov 3Nov 5Nov 9Nov 13Nov 18
20°FNov 1Nov 4Nov 7Nov 11Nov 13Nov 16Nov 20Nov 25Dec 1
16°FNov 8Nov 13Nov 17Nov 21Nov 26Nov 30Dec 3Dec 7Dec 14

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°F172166161157154149145140134
32°F191184179176172168164159153
28°F213205201197193189185179173
24°F235227222218214210206202195
20°F259251245239235230226221214
16°F283275269263258253248242235

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
5,010
Cooling degree days, base 65°F
969
Growing degree days, base 40°F
5,997
Growing degree days, base 45°F
4,709
Growing degree days, base 50°F
3,561
Growing degree days, base 55°F
2,548
Growing degree days, base 60°F
1,683

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,03807
February857011
March675152
April34212187
May12467411
June14200636
July2296759
August4258719
September58121514
October31813205
November637151
December94109

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 7.4 km from Grayson 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 USC00154703 (Leitchfield 2 N). Public domain.