Glen Allen climate

Glen Allen Frost Dates and Growing Season

NOAA 1991-2020 normals for Ashland, 10.1 km from Glen Allen, elevation 220 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ashland. 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 10 and the first fall freeze around October 29, a growing season of about 201 days.

Median at 36°F
last April 24, first October 19
Median at 32°F
last April 10, first October 29
Median at 28°F
last March 30, first November 8

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

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 7Oct 12Oct 15Oct 17Oct 19Oct 22Oct 24Oct 27Nov 1
32°FOct 16Oct 21Oct 24Oct 26Oct 29Nov 1Nov 3Nov 5Nov 10
28°FOct 26Oct 31Nov 2Nov 5Nov 8Nov 10Nov 13Nov 17Nov 25
24°FNov 5Nov 10Nov 13Nov 17Nov 20Nov 24Nov 29Dec 3Dec 9
20°FNov 16Nov 22Nov 28Dec 1Dec 5Dec 8Dec 14Dec 21Dec 28
16°FDec 1Dec 7Dec 12Dec 19Dec 24Dec 29Jan 2Jan 9Jan 18

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°F197191187183179175170165159
32°F219213208205201197193188182
28°F246238232227223219215211204
24°F273265259255250245240233225
20°F304294287281276270264258249
16°F332322313307302296290282271

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
99% 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
3,995
Cooling degree days, base 65°F
1,302
Growing degree days, base 40°F
6,889
Growing degree days, base 45°F
5,460
Growing degree days, base 50°F
4,186
Growing degree days, base 55°F
3,067
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
January868016
February699023
March538596
April24135270
May87105485
June9251691
July0377842
August1331795
September35166581
October23729276
November506285
December774126

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 10.1 km from Glen Allen. 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 USC00440327 (Ashland). Public domain.