Williamsburg climate

Williamsburg Frost Dates and Growing Season

NOAA 1991-2020 normals for Williamsburg, 1.4 km from Williamsburg, elevation 940 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Williamsburg. 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 21 and the first fall freeze around October 22, a growing season of about 182 days.

Median at 36°F
last April 30, first October 13
Median at 32°F
last April 21, first October 22
Median at 28°F
last April 11, first November 1

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 12May 8May 5May 2Apr 30Apr 27Apr 24Apr 21Apr 18
32°FMay 5Apr 30Apr 27Apr 24Apr 21Apr 19Apr 16Apr 13Apr 8
28°FApr 26Apr 21Apr 17Apr 14Apr 11Apr 8Apr 5Apr 1Mar 27
24°FApr 16Apr 9Apr 5Apr 2Mar 31Mar 28Mar 23Mar 19Mar 13
20°FApr 5Mar 31Mar 26Mar 21Mar 18Mar 14Mar 9Mar 4Feb 25
16°FMar 25Mar 18Mar 12Mar 7Mar 2Feb 28Feb 23Feb 15Feb 7

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

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°F184177172168164161157152146
32°F201195190186182179175170164
28°F225216211207203199195190182
24°F251242236230226220216211203
20°F278269262255250245239232224
16°F308298291283277271264257248

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
4,446
Cooling degree days, base 65°F
1,058
Growing degree days, base 40°F
6,364
Growing degree days, base 45°F
4,990
Growing degree days, base 50°F
3,774
Growing degree days, base 55°F
2,716
Growing degree days, base 60°F
1,809

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January928011
February759012
March587374
April31916208
May10886447
June12237675
July0318783
August2264727
September52115513
October27117241
November577168
December829016

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 1.4 km from Williamsburg. 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 USC00158709 (Williamsburg). Public domain.