Greene County climate

Greene County Frost Dates and Growing Season

NOAA 1991-2020 normals for Jefferson, 2.9 km from Greene County, elevation 1055 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Jefferson. 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 9, a growing season of about 164 days.

Median at 36°F
last May 4, first September 29
Median at 32°F
last April 26, first October 9
Median at 28°F
last April 15, first October 21

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

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 16Sep 21Sep 24Sep 27Sep 29Oct 1Oct 5Oct 8Oct 13
32°FSep 23Sep 28Oct 1Oct 5Oct 9Oct 12Oct 16Oct 19Oct 24
28°FOct 3Oct 11Oct 15Oct 19Oct 21Oct 24Oct 26Oct 29Nov 2
24°FOct 16Oct 21Oct 25Oct 28Oct 30Nov 1Nov 3Nov 6Nov 11
20°FOct 25Oct 30Nov 1Nov 3Nov 6Nov 9Nov 11Nov 15Nov 20
16°FNov 1Nov 5Nov 9Nov 11Nov 14Nov 18Nov 22Nov 25Dec 1

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°F165159155150147143139134128
32°F185179173168164160156151144
28°F206199195190185180176170164
24°F226218213210206202198193185
20°F245238232227222218214209202
16°F264256250245240236231226218

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
7,002
Cooling degree days, base 65°F
768
Growing degree days, base 40°F
5,031
Growing degree days, base 45°F
3,941
Growing degree days, base 50°F
2,966
Growing degree days, base 55°F
2,105
Growing degree days, base 60°F
1,368

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,44600
February1,17901
March911121
April512593
May20547324
June27174597
July6257716
August15196646
September12477409
October44511142
November869016
December1,26501

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 2.9 km from Greene 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 USC00134228 (Jefferson). Public domain.