Spotsylvania County climate

Spotsylvania County Frost Dates and Growing Season

NOAA 1991-2020 normals for Fredericksburg Sewage, 21.2 km from Spotsylvania County, elevation 60 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Fredericksburg Sewage. 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 6 and the first fall freeze around November 1, a growing season of about 207 days.

Median at 36°F
last April 21, first October 22
Median at 32°F
last April 6, first November 1
Median at 28°F
last March 27, first November 11

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 8May 3Apr 28Apr 24Apr 21Apr 18Apr 14Apr 10Apr 5
32°FApr 22Apr 17Apr 13Apr 9Apr 6Apr 4Apr 1Mar 29Mar 23
28°FApr 8Apr 4Apr 1Mar 30Mar 27Mar 23Mar 20Mar 16Mar 11
24°FMar 31Mar 25Mar 21Mar 18Mar 15Mar 12Mar 8Mar 3Feb 26
20°FMar 20Mar 15Mar 10Mar 5Mar 2Feb 27Feb 23Feb 16Feb 8
16°FMar 9Mar 3Feb 27Feb 22Feb 17Feb 12Feb 7Feb 1Jan 23

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 10Oct 14Oct 17Oct 20Oct 22Oct 25Oct 27Oct 30Nov 3
32°FOct 19Oct 24Oct 27Oct 29Nov 1Nov 2Nov 5Nov 8Nov 12
28°FOct 30Nov 2Nov 5Nov 8Nov 11Nov 13Nov 16Nov 21Nov 28
24°FNov 8Nov 12Nov 16Nov 20Nov 24Nov 28Dec 1Dec 5Dec 12
20°FNov 19Nov 25Dec 1Dec 4Dec 7Dec 12Dec 17Dec 23Dec 31
16°FDec 5Dec 11Dec 18Dec 23Dec 28Jan 1Jan 3Jan 11Jan 19

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°F203195191187184179175170163
32°F225219215210207204200195187
28°F253243239235230226221217211
24°F279270264259254249244239231
20°F307299292287281276271264256
16°F337327320313308303298290281

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
98% 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
4,300
Cooling degree days, base 65°F
1,336
Growing degree days, base 40°F
6,695
Growing degree days, base 45°F
5,317
Growing degree days, base 50°F
4,097
Growing degree days, base 55°F
3,028
Growing degree days, base 60°F
2,107

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January914011
February753013
March614262
April29324220
May10292456
June10268708
July0405869
August1349814
September30168588
October24228270
November540167
December801019

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 21.2 km from Spotsylvania 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 USC00443204 (Fredericksburg Sewage). Public domain.