Savannah climate

Savannah Frost Dates and Growing Season

NOAA 1991-2020 normals for Cosby 2W, 14.3 km from Savannah, elevation 910 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Cosby 2W. 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 17 and the first fall freeze around October 19, a growing season of about 184 days.

Median at 36°F
last April 28, first October 9
Median at 32°F
last April 17, first October 19
Median at 28°F
last April 7, first October 28

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 9May 6May 3Apr 30Apr 28Apr 25Apr 22Apr 18Apr 14
32°FMay 1Apr 26Apr 23Apr 20Apr 17Apr 14Apr 11Apr 8Apr 3
28°FApr 21Apr 16Apr 13Apr 10Apr 7Apr 4Apr 1Mar 30Mar 22
24°FApr 12Apr 7Apr 3Mar 31Mar 28Mar 24Mar 20Mar 16Mar 9
20°FApr 2Mar 29Mar 24Mar 21Mar 18Mar 14Mar 11Mar 6Mar 2
16°FMar 27Mar 19Mar 15Mar 11Mar 8Mar 5Mar 2Feb 27Feb 21

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°FSep 25Sep 30Oct 3Oct 6Oct 9Oct 12Oct 15Oct 18Oct 22
32°FOct 4Oct 10Oct 14Oct 17Oct 19Oct 22Oct 24Oct 27Oct 30
28°FOct 16Oct 20Oct 23Oct 26Oct 28Oct 31Nov 1Nov 5Nov 9
24°FOct 24Oct 29Nov 1Nov 3Nov 6Nov 8Nov 11Nov 15Nov 20
20°FNov 1Nov 5Nov 9Nov 12Nov 15Nov 18Nov 22Nov 26Dec 2
16°FNov 9Nov 14Nov 18Nov 22Nov 26Nov 29Dec 3Dec 7Dec 14

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°F183177172168165161157152145
32°F203197193188184181178173166
28°F223216212208205201197192187
24°F246239232228223219215210202
20°F268260253248243238232227218
16°F285278272267263258252245238

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
100% 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
5,718
Cooling degree days, base 65°F
1,167
Growing degree days, base 40°F
5,937
Growing degree days, base 45°F
4,721
Growing degree days, base 50°F
3,638
Growing degree days, base 55°F
2,690
Growing degree days, base 60°F
1,865

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,22100
February98406
March733249
April3998150
May15380403
June9256697
July1371835
August3298759
September75132508
October34919200
November720030
December1,07101

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 14.3 km from Savannah. 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 USC00231924 (Cosby 2W). Public domain.