Nelson County climate

Nelson County Frost Dates and Growing Season

NOAA 1991-2020 normals for Petersburg 2 N, 18.5 km from Nelson County, elevation 1532 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Petersburg 2 N. 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 11 and the first fall freeze around September 28, a growing season of about 138 days.

Median at 36°F
last May 21, first September 20
Median at 32°F
last May 11, first September 28
Median at 28°F
last May 2, first October 7

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

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 7Sep 12Sep 15Sep 18Sep 20Sep 22Sep 24Sep 27Oct 1
32°FSep 16Sep 21Sep 23Sep 26Sep 28Sep 30Oct 3Oct 6Oct 10
28°FSep 25Sep 28Oct 1Oct 4Oct 7Oct 10Oct 13Oct 17Oct 21
24°FOct 1Oct 6Oct 11Oct 14Oct 17Oct 21Oct 24Oct 27Oct 30
20°FOct 13Oct 17Oct 21Oct 25Oct 28Oct 30Nov 1Nov 5Nov 8
16°FOct 21Oct 26Oct 30Nov 1Nov 4Nov 6Nov 8Nov 11Nov 15

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°F137132128124120117114109101
32°F155150145141138134130125119
28°F176169164160156152148144137
24°F194187183179176172167162155
20°F213207202197193189186180173
16°F226219214211207203199195189

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
9,920
Cooling degree days, base 65°F
344
Growing degree days, base 40°F
3,653
Growing degree days, base 45°F
2,767
Growing degree days, base 50°F
1,982
Growing degree days, base 55°F
1,306
Growing degree days, base 60°F
751

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,86800
February1,56900
March1,32501
April779024
May37213182
June10667414
July35135564
August55104515
September26324244
October714138
November1,18401
December1,65100

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 18.5 km from Nelson County. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00327027 (Petersburg 2 N). Public domain.