Macon County climate

Macon County Frost Dates and Growing Season

NOAA 1991-2020 normals for Decatur Wtp, 3.6 km from Macon County, elevation 639 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Decatur Wtp. 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 14 and the first fall freeze around October 24, a growing season of about 192 days.

Median at 36°F
last April 26, first October 14
Median at 32°F
last April 14, first October 24
Median at 28°F
last April 3, first November 3

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

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 30Oct 5Oct 8Oct 11Oct 14Oct 16Oct 19Oct 22Oct 27
32°FOct 11Oct 15Oct 18Oct 21Oct 24Oct 27Oct 30Nov 1Nov 5
28°FOct 20Oct 26Oct 30Nov 1Nov 3Nov 6Nov 9Nov 12Nov 19
24°FOct 30Nov 3Nov 6Nov 9Nov 12Nov 15Nov 19Nov 25Dec 1
20°FNov 7Nov 11Nov 15Nov 19Nov 23Nov 27Dec 1Dec 5Dec 12
16°FNov 13Nov 19Nov 24Nov 29Dec 2Dec 6Dec 11Dec 18Dec 23

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°F190183178174170166161155147
32°F211205200196192188183178171
28°F237230224218214211207202195
24°F258250245239236231226220213
20°F281271265259254250244239231
16°F298289283277272267262255246

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
5,443
Cooling degree days, base 65°F
1,116
Growing degree days, base 40°F
6,002
Growing degree days, base 45°F
4,767
Growing degree days, base 50°F
3,664
Growing degree days, base 55°F
2,685
Growing degree days, base 60°F
1,834

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,18201
February94405
March721247
April36212171
May12886428
June12241679
July1330794
August3289750
September64135522
October31621220
November682144
December1,02904

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 3.6 km from Macon County. 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 USC00112193 (Decatur Wtp). Public domain.