Mobile climate

Mobile Frost Dates and Growing Season

NOAA 1991-2020 normals for Mobile Dwtn AP, 7.9 km from Mobile, elevation 26 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Mobile Dwtn AP. 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 21 and the first fall freeze around December 6, a growing season of about 292 days.

Median at 36°F
last March 6, first November 22
Median at 32°F
last February 21, first December 6
Median at 28°F
last February 2, first December 30

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 25Mar 20Mar 14Mar 11Mar 6Mar 2Feb 25Feb 19Feb 12
32°FMar 15Mar 9Mar 3Feb 27Feb 21Feb 15Feb 9Feb 2Jan 25
28°FMar 6Feb 24Feb 15Feb 7Feb 2Jan 29Jan 24Jan 15Jan 2
24°FFeb 23Feb 8Feb 1Jan 28Jan 22Jan 17Jan 11Jan 4Dec 27
20°FFeb 6Feb 1Jan 27Jan 21Jan 17Jan 13Jan 6Jan 1Dec 24
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 5Nov 11Nov 15Nov 19Nov 22Nov 27Dec 1Dec 5Dec 13
32°FNov 15Nov 22Nov 28Dec 1Dec 6Dec 12Dec 19Dec 28Jan 5
28°FNov 30Dec 7Dec 14Dec 23Dec 30Jan 3Jan 8Jan 16Jan 30
24°FDec 14Dec 25Jan 1Jan 3Jan 9Jan 14Jan 20Jan 29Feb 6
20°FDec 20Dec 30Jan 2Jan 8Jan 14Jan 17Jan 21Jan 30Feb 4
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°F294283277269264258251245236
32°F326314305298292286279271257
28°F361350340334326318310301288
24°F365365365365359351341332317
20°F365365365365365365365365351
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
100% of years
28°F or colder
89% of years
24°F or colder
59% of years
20°F or colder
21% of years
16°F or colder
2% 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
1,404
Cooling degree days, base 65°F
2,931
Growing degree days, base 40°F
10,672
Growing degree days, base 45°F
8,894
Growing degree days, base 50°F
7,192
Growing degree days, base 55°F
5,612
Growing degree days, base 60°F
4,185

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January4028156
February27016199
March15152373
April38135548
May2332795
June0496946
July05741,039
August05771,042
September0459909
October30221656
November17346332
December33815198

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 7.9 km from Mobile. 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 USW00013838 (Mobile Dwtn AP). Public domain.