Clark County climate

Clark County Frost Dates and Growing Season

NOAA 1991-2020 normals for Small 6N, 4.8 km from Clark County, elevation 5740 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Small 6N. 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 June 5 and the first fall freeze around September 20, a growing season of about 106 days.

Median at 36°F
last June 18, first September 8
Median at 32°F
last June 5, first September 20
Median at 28°F
last May 10, first October 2

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°FJul 2Jun 28Jun 24Jun 21Jun 18Jun 15Jun 13Jun 9Jun 5
32°FJun 21Jun 16Jun 12Jun 8Jun 5May 31May 25May 19May 11
28°FJun 8May 30May 19May 14May 10May 7May 3May 1Apr 25
24°FMay 9May 3May 1Apr 28Apr 24Apr 22Apr 18Apr 14Apr 9
20°FApr 27Apr 21Apr 17Apr 14Apr 10Apr 7Apr 4Mar 31Mar 23
16°FApr 14Apr 8Apr 4Mar 31Mar 28Mar 22Mar 18Mar 13Mar 9

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

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°F999288837975716558
32°F133123116111106102979081
28°F163157153148143137132125113
24°F191183177173169165161156148
20°F217209203199194190187182175
16°F242235230225219214209203195

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
8,387
Cooling degree days, base 65°F
208
Growing degree days, base 40°F
3,347
Growing degree days, base 45°F
2,423
Growing degree days, base 50°F
1,650
Growing degree days, base 55°F
1,017
Growing degree days, base 60°F
531

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,40400
February1,18200
March99100
April686011
May4191111
June21315265
July44108528
August5376489
September2748215
October696029
November1,05201
December1,37500

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 4.8 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 USC00108500 (Small 6N). Public domain.