Dauphin Island climate

Dauphin Island Frost Dates and Growing Season

NOAA 1991-2020 normals for Dauphin Is #2, 3.2 km from Dauphin Island, elevation 8 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Dauphin Is #2. 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 January 31 and the first fall freeze around January 6, a growing season of about 340 days.

Median at 36°F
last February 11, first December 28
Median at 32°F
last January 31, first January 6
Median at 28°F
last January 21, first January 13

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 10Mar 1Feb 24Feb 17Feb 11Feb 6Feb 1Jan 25Jan 14
32°FFeb 27Feb 17Feb 8Feb 2Jan 31Jan 24Jan 17Jan 11Jan 1
28°FFeb 11Feb 4Feb 1Jan 28Jan 21Jan 17Jan 11Jan 3Dec 26
24°FFeb 7Feb 2Feb 1Jan 29Jan 21Jan 16Jan 13Jan 6Jan 1
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 27Dec 7Dec 14Dec 22Dec 28Jan 1Jan 5Jan 12Jan 21
32°FDec 12Dec 21Dec 29Jan 1Jan 6Jan 12Jan 17Jan 25Feb 2
28°FDec 20Dec 30Jan 3Jan 9Jan 13Jan 17Jan 23Jan 31Feb 4
24°FDec 30Jan 2Jan 9Jan 13Jan 17Jan 23Jan 30Feb 1Feb 6
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°F345333326319313305298287272
32°F365365355347340334328320305
28°F365365365365365361350342331
24°F365365365365365365365365353
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
98% of years
32°F or colder
79% of years
28°F or colder
44% of years
24°F or colder
15% of years
20°F or colder
2% 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
1,323
Cooling degree days, base 65°F
2,883
Growing degree days, base 40°F
10,699
Growing degree days, base 45°F
8,910
Growing degree days, base 50°F
7,183
Growing degree days, base 55°F
5,576
Growing degree days, base 60°F
4,134

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January3942141
February2724181
March14732358
April31130549
May1342806
June0489939
July05641,029
August05641,029
September0461910
October19238684
November14748359
December3129198

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 3.2 km from Dauphin Island. 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 USC00012172 (Dauphin Is #2). Public domain.