Clemson climate

Clemson Frost Dates and Growing Season

NOAA 1991-2020 normals for Clemson Univ, 2.8 km from Clemson, elevation 800 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Clemson Univ. 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 1 and the first fall freeze around November 3, a growing season of about 217 days.

Median at 36°F
last April 14, first October 25
Median at 32°F
last April 1, first November 3
Median at 28°F
last March 19, first November 13

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°FApr 30Apr 24Apr 21Apr 17Apr 14Apr 11Apr 6Apr 3Mar 29
32°FApr 18Apr 11Apr 7Apr 3Apr 1Mar 30Mar 26Mar 22Mar 16
28°FApr 6Mar 31Mar 28Mar 23Mar 19Mar 15Mar 11Mar 5Feb 26
24°FMar 24Mar 18Mar 14Mar 10Mar 4Feb 28Feb 23Feb 16Feb 3
20°FMar 15Mar 7Feb 28Feb 21Feb 15Feb 7Jan 31Jan 24Jan 13
16°FMar 2Feb 18Feb 7Feb 1Jan 27Jan 21Jan 15Jan 8Dec 31

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 12Oct 17Oct 20Oct 23Oct 25Oct 28Oct 30Nov 2Nov 6
32°FOct 21Oct 25Oct 29Nov 1Nov 3Nov 5Nov 8Nov 12Nov 17
28°FOct 31Nov 4Nov 7Nov 10Nov 13Nov 16Nov 20Nov 25Dec 3
24°FNov 10Nov 14Nov 19Nov 25Nov 29Dec 3Dec 6Dec 13Dec 27
20°FNov 23Dec 1Dec 4Dec 9Dec 18Dec 25Jan 1Jan 7Jan 18
16°FDec 6Dec 18Dec 26Jan 1Jan 4Jan 11Jan 16Jan 23Feb 5

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°F215209204199195191187182174
32°F239231226221217213208203197
28°F268258252247241237231226217
24°F306292284277269264257251244
20°F343332323312306299292283270
16°F365365355346339332324314303

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
97% of years
16°F or colder
80% 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
2,989
Cooling degree days, base 65°F
1,743
Growing degree days, base 40°F
8,032
Growing degree days, base 45°F
6,437
Growing degree days, base 50°F
5,008
Growing degree days, base 55°F
3,750
Growing degree days, base 60°F
2,661

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January684035
February537148
March3928157
April16941332
May39160586
June2342790
July0457922
August0422887
September11252691
October14354384
November3985128
December616146

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 2.8 km from Clemson. 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 USC00381770 (Clemson Univ). Public domain.