Summerville climate

Summerville Frost Dates and Growing Season

NOAA 1991-2020 normals for Summerville, 4.8 km from Summerville, elevation 639 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Summerville. 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 7 and the first fall freeze around October 30, a growing season of about 204 days.

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

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 9Oct 13Oct 16Oct 18Oct 21Oct 23Oct 26Oct 29Nov 1
32°FOct 18Oct 22Oct 25Oct 27Oct 30Nov 1Nov 3Nov 6Nov 10
28°FOct 26Oct 31Nov 1Nov 5Nov 7Nov 10Nov 14Nov 18Nov 25
24°FNov 4Nov 8Nov 11Nov 15Nov 19Nov 24Nov 28Dec 2Dec 13
20°FNov 12Nov 19Nov 25Nov 30Dec 4Dec 10Dec 20Dec 30Jan 8
16°FNov 26Dec 4Dec 15Dec 25Jan 1Jan 5Jan 11Jan 18Feb 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°F205198192188185181177171164
32°F225218213208204200196191184
28°F253243236231227222217212206
24°F284274266259253248242236228
20°F322310302294287279272262252
16°F361346337331324315306299287

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
91% 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
3,395
Cooling degree days, base 65°F
1,527
Growing degree days, base 40°F
7,515
Growing degree days, base 45°F
5,978
Growing degree days, base 50°F
4,608
Growing degree days, base 55°F
3,415
Growing degree days, base 60°F
2,396

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January759028
February588035
March4443118
April20725285
May57127535
June1300748
July0418883
August0391856
September16217651
October18042339
November471390
December670040

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 4.8 km from Summerville. 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 USC00098436 (Summerville). Public domain.