Jefferson climate

Jefferson Frost Dates and Growing Season

NOAA 1991-2020 normals for Charleston WFO, 8.7 km from Jefferson, elevation 918 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Charleston WFO. 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 23 and the first fall freeze around October 20, a growing season of about 180 days.

Median at 36°F
last May 4, first October 11
Median at 32°F
last April 23, first October 20
Median at 28°F
last April 10, first October 30

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 22May 16May 11May 7May 4May 1Apr 28Apr 24Apr 20
32°FMay 13May 5Apr 30Apr 27Apr 23Apr 20Apr 17Apr 14Apr 9
28°FApr 29Apr 21Apr 16Apr 13Apr 10Apr 7Apr 5Apr 1Mar 28
24°FApr 13Apr 8Apr 4Apr 1Mar 31Mar 27Mar 23Mar 19Mar 12
20°FApr 2Mar 29Mar 25Mar 22Mar 19Mar 15Mar 11Mar 5Feb 25
16°FMar 24Mar 18Mar 14Mar 10Mar 6Mar 1Feb 26Feb 18Feb 8

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 30Oct 3Oct 6Oct 9Oct 11Oct 13Oct 15Oct 18Oct 22
32°FOct 8Oct 12Oct 15Oct 18Oct 20Oct 22Oct 25Oct 28Nov 1
28°FOct 17Oct 21Oct 24Oct 27Oct 30Nov 1Nov 3Nov 6Nov 12
24°FOct 27Nov 1Nov 4Nov 6Nov 10Nov 12Nov 15Nov 19Nov 26
20°FNov 5Nov 10Nov 14Nov 17Nov 21Nov 26Nov 30Dec 3Dec 10
16°FNov 14Nov 21Nov 27Dec 1Dec 4Dec 8Dec 13Dec 21Dec 29

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°F179172167163159156151146139
32°F198192188184180175170165157
28°F220215210206201197194189180
24°F249239234229225221217213208
20°F278269261256250245238234226
16°F308297290284277272265258249

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
4,846
Cooling degree days, base 65°F
1,018
Growing degree days, base 40°F
6,134
Growing degree days, base 45°F
4,820
Growing degree days, base 50°F
3,656
Growing degree days, base 55°F
2,635
Growing degree days, base 60°F
1,751

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,001013
February821015
March678461
April33522208
May13082424
June16203637
July1303767
August3265727
September58121514
October31718215
November616154
December871020

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 8.7 km from Jefferson. 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 USC00461579 (Charleston WFO). Public domain.