Clark County climate

Clark County Frost Dates and Growing Season

NOAA 1991-2020 normals for Clark, 2.6 km from Clark County, elevation 1804 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Clark. 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 May 5 and the first fall freeze around October 5, a growing season of about 153 days.

Median at 36°F
last May 13, first September 27
Median at 32°F
last May 5, first October 5
Median at 28°F
last April 26, first October 15

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 26May 21May 18May 16May 13May 11May 8May 5May 2
32°FMay 18May 13May 10May 7May 5May 3Apr 30Apr 27Apr 22
28°FMay 8May 4May 2Apr 30Apr 26Apr 23Apr 20Apr 17Apr 12
24°FMay 1Apr 27Apr 22Apr 19Apr 16Apr 13Apr 10Apr 7Apr 3
20°FApr 21Apr 16Apr 12Apr 9Apr 6Apr 4Apr 2Mar 29Mar 22
16°FApr 14Apr 8Apr 4Apr 2Mar 31Mar 27Mar 23Mar 18Mar 13

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

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°F151146141138135132129124119
32°F170164160156153149145141135
28°F190184178174170167163159153
24°F209202198193189185181176170
20°F228221215211206202198194187
16°F243236231227222218214208202

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
8,486
Cooling degree days, base 65°F
540
Growing degree days, base 40°F
4,233
Growing degree days, base 45°F
3,259
Growing degree days, base 50°F
2,402
Growing degree days, base 55°F
1,654
Growing degree days, base 60°F
1,030

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,63400
February1,35800
March1,12205
April679139
May31318219
June68104486
July17209657
August29156592
September19050326
October596373
November1,03104
December1,45100

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 2.6 km from Clark 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 USC00391739 (Clark). Public domain.