Louisa County climate

Louisa County Frost Dates and Growing Season

NOAA 1991-2020 normals for Louisa, 8.1 km from Louisa County, elevation 420 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Louisa. 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 26 and the first fall freeze around October 20, a growing season of about 175 days.

Median at 36°F
last May 6, first October 10
Median at 32°F
last April 26, first October 20
Median at 28°F
last April 12, 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 23May 18May 12May 9May 6May 3Apr 30Apr 27Apr 21
32°FMay 13May 6May 2Apr 29Apr 26Apr 22Apr 19Apr 15Apr 9
28°FApr 30Apr 22Apr 18Apr 15Apr 12Apr 8Apr 4Mar 31Mar 27
24°FApr 14Apr 9Apr 5Apr 2Mar 30Mar 27Mar 24Mar 19Mar 12
20°FApr 3Mar 30Mar 26Mar 23Mar 19Mar 15Mar 10Mar 4Feb 26
16°FMar 24Mar 18Mar 14Mar 9Mar 4Feb 28Feb 24Feb 19Feb 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 27Oct 1Oct 4Oct 7Oct 10Oct 12Oct 15Oct 18Oct 23
32°FOct 7Oct 11Oct 14Oct 17Oct 20Oct 23Oct 25Oct 28Nov 1
28°FOct 15Oct 21Oct 24Oct 27Oct 29Nov 1Nov 3Nov 6Nov 10
24°FOct 26Oct 31Nov 3Nov 5Nov 8Nov 11Nov 14Nov 18Nov 25
20°FNov 5Nov 11Nov 14Nov 18Nov 21Nov 26Dec 1Dec 4Dec 13
16°FNov 17Nov 24Nov 29Dec 3Dec 7Dec 12Dec 18Dec 26Jan 2

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°F174168164160156151147142134
32°F196190185180175171167161153
28°F221214209204200196192187179
24°F247238232228224220216211203
20°F277268261255250245240234226
16°F309299292286280275268261252

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
4,448
Cooling degree days, base 65°F
1,119
Growing degree days, base 40°F
6,382
Growing degree days, base 45°F
5,020
Growing degree days, base 50°F
3,815
Growing degree days, base 55°F
2,763
Growing degree days, base 60°F
1,863

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January921012
February750016
March607268
April29224222
May11281436
June15223658
July1340804
August2295758
September52132530
October28421232
November579161
December834018

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 8.1 km from Louisa 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 USC00445050 (Louisa). Public domain.