Mount Pleasant climate

Mount Pleasant Frost Dates and Growing Season

NOAA 1991-2020 normals for Sullivans Is, 3.6 km from Mount Pleasant, elevation 5 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Sullivans Is. 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 March 13 and the first fall freeze around November 30, a growing season of about 262 days.

Median at 36°F
last March 25, first November 16
Median at 32°F
last March 13, first November 30
Median at 28°F
last March 1, first December 16

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 10Apr 5Apr 1Mar 29Mar 25Mar 21Mar 17Mar 13Mar 6
32°FMar 30Mar 25Mar 21Mar 17Mar 13Mar 9Mar 4Feb 28Feb 19
28°FMar 22Mar 16Mar 10Mar 5Mar 1Feb 25Feb 17Feb 9Feb 1
24°FMar 13Mar 4Feb 27Feb 17Feb 9Feb 2Jan 29Jan 21Jan 9
20°FMar 4Feb 20Feb 7Jan 31Jan 27Jan 21Jan 15Jan 9Jan 2
16°FFeb 21Feb 2Jan 29Jan 24Jan 17Jan 13Jan 8Jan 4Dec 29

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 1Nov 5Nov 9Nov 12Nov 16Nov 19Nov 24Nov 29Dec 5
32°FNov 11Nov 17Nov 21Nov 26Nov 30Dec 2Dec 8Dec 14Dec 24
28°FNov 25Dec 1Dec 5Dec 11Dec 16Dec 21Dec 27Jan 2Jan 10
24°FDec 5Dec 15Dec 22Dec 28Jan 2Jan 7Jan 12Jan 18Jan 29
20°FDec 18Dec 26Jan 1Jan 5Jan 9Jan 14Jan 20Jan 27Feb 8
16°FDec 22Dec 30Jan 4Jan 8Jan 13Jan 17Jan 23Jan 29Feb 7

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°F263253246241236230225219212
32°F291281274268262256250243232
28°F320309301295288283277270259
24°F356343334327317309302295285
20°F365365365356347339333318304
16°F365365365365365365362349336

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
97% of years
20°F or colder
73% of years
16°F or colder
37% 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
2,051
Cooling degree days, base 65°F
2,279
Growing degree days, base 40°F
9,400
Growing degree days, base 45°F
7,670
Growing degree days, base 50°F
6,058
Growing degree days, base 55°F
4,612
Growing degree days, base 60°F
3,353

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January532071
February415084
March2897213
April9166426
May9248704
June1418867
July0529994
August0496961
September1355804
October47137556
November22922261
December4383118

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 3.6 km from Mount Pleasant. 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 USC00388405 (Sullivans Is). Public domain.