Washington County climate

Washington County Frost Dates and Growing Season

NOAA 1991-2020 normals for Wesley, 5 km from Washington County, elevation 410 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Wesley. 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 2 and the first fall freeze around October 15, a growing season of about 164 days.

Median at 36°F
last May 12, first October 2
Median at 32°F
last May 2, first October 15
Median at 28°F
last April 21, first October 29

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 15May 12May 10May 7May 5May 1
32°FMay 12May 8May 5May 3May 2Apr 30Apr 28Apr 25Apr 21
28°FApr 30Apr 28Apr 25Apr 23Apr 21Apr 18Apr 16Apr 13Apr 8
24°FApr 22Apr 19Apr 16Apr 13Apr 10Apr 8Apr 6Apr 3Apr 1
20°FApr 15Apr 10Apr 7Apr 4Apr 2Apr 1Mar 30Mar 25Mar 19
16°FApr 7Apr 4Apr 1Mar 31Mar 28Mar 24Mar 20Mar 17Mar 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 21Sep 25Sep 28Oct 1Oct 2Oct 5Oct 8Oct 11Oct 17
32°FOct 1Oct 4Oct 8Oct 11Oct 15Oct 18Oct 21Oct 25Oct 30
28°FOct 13Oct 19Oct 22Oct 26Oct 29Nov 1Nov 2Nov 6Nov 10
24°FOct 26Nov 1Nov 3Nov 6Nov 9Nov 11Nov 14Nov 17Nov 22
20°FNov 5Nov 10Nov 13Nov 16Nov 18Nov 21Nov 23Nov 27Dec 1
16°FNov 14Nov 18Nov 22Nov 25Nov 27Nov 30Dec 1Dec 5Dec 11

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°F159153149145142138134129123
32°F183177173168164161157152146
28°F208202196193189185182176171
24°F229223218215211208204200194
20°F248242237233230227223219213
16°F265258253249245242237233227

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
7,761
Cooling degree days, base 65°F
260
Growing degree days, base 40°F
3,781
Growing degree days, base 45°F
2,791
Growing degree days, base 50°F
1,934
Growing degree days, base 55°F
1,220
Growing degree days, base 60°F
654

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,42600
February1,22800
March1,08802
April714013
May3753137
June12535361
July27107546
August3695524
September19820278
October522168
November83405
December1,18900

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 5 km from Washington 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 USC00179294 (Wesley). Public domain.