Marengo County climate

Marengo County Frost Dates and Growing Season

NOAA 1991-2020 normals for Demopolis L&d, 31.3 km from Marengo County, elevation 100 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Demopolis L&d. 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 16 and the first fall freeze around November 14, a growing season of about 241 days.

Median at 36°F
last March 29, first November 3
Median at 32°F
last March 16, first November 14
Median at 28°F
last March 2, first November 26

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 14Apr 8Apr 5Apr 1Mar 29Mar 25Mar 21Mar 17Mar 11
32°FApr 3Mar 27Mar 23Mar 19Mar 16Mar 12Mar 7Mar 3Feb 26
28°FMar 19Mar 14Mar 8Mar 5Mar 2Feb 28Feb 23Feb 17Feb 9
24°FMar 9Mar 2Feb 26Feb 20Feb 14Feb 8Feb 2Jan 27Jan 18
20°FFeb 28Feb 18Feb 9Feb 2Jan 30Jan 24Jan 16Jan 7Dec 24
16°FFeb 15Feb 7Feb 2Jan 29Jan 24Jan 17Jan 9Jan 2Dec 22

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 26Oct 29Nov 1Nov 3Nov 6Nov 9Nov 13Nov 19
32°FOct 31Nov 3Nov 7Nov 10Nov 14Nov 17Nov 20Nov 25Dec 1
28°FNov 9Nov 14Nov 18Nov 21Nov 26Nov 30Dec 3Dec 9Dec 21
24°FNov 18Nov 26Dec 1Dec 4Dec 10Dec 18Dec 29Jan 4Jan 15
20°FNov 26Dec 6Dec 13Dec 22Dec 30Jan 2Jan 10Jan 18Feb 1
16°FDec 6Dec 19Dec 28Jan 1Jan 7Jan 14Jan 23Feb 1Feb 6

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°F242234229224219215209204196
32°F268259253247241236230225217
28°F302290281275270264258251243
24°F338325316307302295286278266
20°F365358347337331324315306296
16°F365365365365365358346335323

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
49% 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
2,467
Cooling degree days, base 65°F
2,205
Growing degree days, base 40°F
8,982
Growing degree days, base 45°F
7,330
Growing degree days, base 50°F
5,813
Growing degree days, base 55°F
4,447
Growing degree days, base 60°F
3,244

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January613267
February454490
March28823240
April11072415
May15237687
June0407856
July0508973
August0493958
September3336783
October99107477
November33913182
December545486

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 31.3 km from Marengo County. 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 USC00012245 (Demopolis L&d). Public domain.