Folly Beach climate

Folly Beach Frost Dates and Growing Season

NOAA 1991-2020 normals for Charleston City, 13.9 km from Folly Beach, elevation 10 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Charleston City. 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 February 4 and the first fall freeze around December 30, a growing season of about 321 days.

Median at 36°F
last February 25, first December 10
Median at 32°F
last February 4, first December 30
Median at 28°F
last January 24, first January 8

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°FMar 17Mar 11Mar 6Mar 2Feb 25Feb 20Feb 13Feb 6Jan 29
32°FMar 4Feb 25Feb 17Feb 10Feb 4Jan 30Jan 24Jan 16Jan 5
28°FFeb 20Feb 9Feb 1Jan 28Jan 24Jan 15Jan 10Jan 4Dec 27
24°FFeb 10Feb 1Jan 28Jan 24Jan 18Jan 14Jan 9Jan 3Dec 30
20°F–––––––––
16°F–––––––––

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°FNov 20Nov 26Dec 1Dec 6Dec 10Dec 17Dec 23Dec 29Jan 7
32°FDec 2Dec 10Dec 20Dec 25Dec 30Jan 3Jan 9Jan 15Jan 25
28°FDec 15Dec 23Dec 30Jan 3Jan 8Jan 13Jan 18Jan 26Feb 3
24°FDec 22Jan 1Jan 6Jan 10Jan 15Jan 19Jan 23Jan 28Feb 2
20°F–––––––––
16°F–––––––––

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°F323311303296290283276269259
32°F357343336329321314307300289
28°F365365365360352344336328314
24°F365365365365365365365358338
20°F365365365365365365365365365
16°F365365365365365365365365365

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
92% of years
28°F or colder
63% of years
24°F or colder
25% of years
20°F or colder
4% of years
16°F or colder
0% 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
1,623
Cooling degree days, base 65°F
2,448
Growing degree days, base 40°F
9,972
Growing degree days, base 45°F
8,203
Growing degree days, base 50°F
6,519
Growing degree days, base 55°F
4,978
Growing degree days, base 60°F
3,615

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January4422116
February3343139
March21321289
April6292481
May6269729
June0428878
July05361,001
August0510975
September1377826
October33169602
November18134313
December3537171

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 13.9 km from Folly Beach. 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 USW00013782 (Charleston City). Public domain.