Barnwell climate

Barnwell Frost Dates and Growing Season

NOAA 1991-2020 normals for Barnwell 5 Ene, 11.5 km from Barnwell, elevation 245 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Barnwell 5 Ene. 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 22 and the first fall freeze around November 9, a growing season of about 233 days.

Median at 36°F
last April 4, first November 1
Median at 32°F
last March 22, first November 9
Median at 28°F
last March 8, first November 20

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 20Apr 15Apr 11Apr 7Apr 4Apr 1Mar 29Mar 24Mar 19
32°FApr 9Apr 3Mar 30Mar 26Mar 22Mar 18Mar 15Mar 9Mar 1
28°FMar 27Mar 22Mar 18Mar 13Mar 8Mar 4Feb 28Feb 21Feb 11
24°FMar 17Mar 10Mar 2Feb 26Feb 17Feb 10Feb 3Jan 30Jan 19
20°FMar 4Feb 21Feb 11Feb 4Jan 31Jan 27Jan 19Jan 12Dec 30
16°FFeb 16Feb 5Jan 31Jan 27Jan 21Jan 15Jan 10Jan 3Dec 25

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 20Oct 25Oct 28Oct 31Nov 1Nov 4Nov 6Nov 9Nov 14
32°FOct 30Nov 1Nov 4Nov 7Nov 9Nov 12Nov 15Nov 19Nov 25
28°FNov 6Nov 10Nov 14Nov 17Nov 20Nov 24Nov 30Dec 5Dec 16
24°FNov 16Nov 22Nov 27Dec 2Dec 7Dec 18Dec 27Jan 3Jan 12
20°FNov 28Dec 6Dec 16Dec 26Jan 1Jan 6Jan 12Jan 17Feb 1
16°FDec 13Dec 24Jan 1Jan 5Jan 10Jan 14Jan 20Jan 28Feb 4

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°F232224219215211207203199192
32°F259249242237233229224218210
28°F294281272265258253247241232
24°F332320311302296288280271259
20°F365353343334329320311302290
16°F365365365365365354343333320

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
99% of years
20°F or colder
85% of years
16°F or colder
50% 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
2,292
Cooling degree days, base 65°F
2,221
Growing degree days, base 40°F
9,148
Growing degree days, base 45°F
7,470
Growing degree days, base 50°F
5,917
Growing degree days, base 55°F
4,514
Growing degree days, base 60°F
3,279

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January566286
February4205112
March28823242
April10576426
May16243693
June0414864
July0524989
August0490955
September4316762
October88108487
November31316195
December4934108

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 11.5 km from Barnwell. 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 USC00380490 (Barnwell 5 Ene). Public domain.