Chester Gap climate

Chester Gap Frost Dates and Growing Season

NOAA 1991-2020 normals for Front Royal, 6.9 km from Chester Gap, elevation 930 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Front Royal. 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 13 and the first fall freeze around October 28, a growing season of about 196 days.

Median at 36°F
last April 30, first October 16
Median at 32°F
last April 13, first October 28
Median at 28°F
last April 2, first November 7

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 18May 11May 6May 2Apr 30Apr 25Apr 20Apr 16Apr 11
32°FMay 5Apr 28Apr 21Apr 17Apr 13Apr 9Apr 6Apr 3Mar 30
28°FApr 17Apr 10Apr 7Apr 4Apr 2Mar 30Mar 27Mar 22Mar 16
24°FApr 5Apr 2Mar 30Mar 26Mar 22Mar 19Mar 15Mar 10Mar 4
20°FMar 30Mar 23Mar 19Mar 16Mar 12Mar 8Mar 4Feb 28Feb 22
16°FMar 19Mar 14Mar 9Mar 5Mar 2Feb 26Feb 21Feb 13Feb 6

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 4Oct 8Oct 12Oct 14Oct 16Oct 20Oct 23Oct 26Oct 31
32°FOct 14Oct 19Oct 23Oct 25Oct 28Oct 31Nov 1Nov 5Nov 9
28°FOct 26Oct 30Nov 2Nov 4Nov 7Nov 10Nov 14Nov 17Nov 22
24°FNov 4Nov 8Nov 13Nov 16Nov 20Nov 24Nov 28Dec 2Dec 8
20°FNov 16Nov 22Nov 27Dec 1Dec 4Dec 8Dec 14Dec 19Dec 25
16°FDec 1Dec 6Dec 11Dec 16Dec 20Dec 25Dec 29Jan 3Jan 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°F193185179174170166161156149
32°F216209205200196192186180170
28°F243236231225221216211206199
24°F269261255249245241235229219
20°F294286279273269263258250241
16°F324313305300295290285277267

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
4,740
Cooling degree days, base 65°F
1,013
Growing degree days, base 40°F
6,109
Growing degree days, base 45°F
4,785
Growing degree days, base 50°F
3,613
Growing degree days, base 55°F
2,589
Growing degree days, base 60°F
1,721

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January975010
February809012
March672254
April33320194
May13769400
June18202634
July1323787
August3267728
September60111502
October29418223
November584154
December854015

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 6.9 km from Chester Gap. 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 USC00443229 (Front Royal). Public domain.