Macon County climate

Macon County Frost Dates and Growing Season

NOAA 1991-2020 normals for Franklin, 4.3 km from Macon County, elevation 2125 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Franklin. 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 23, a growing season of about 187 days.

Median at 36°F
last May 1, first October 14
Median at 32°F
last April 17, first October 23
Median at 28°F
last April 5, first November 1

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

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 2Oct 6Oct 9Oct 12Oct 14Oct 16Oct 19Oct 22Oct 26
32°FOct 11Oct 14Oct 17Oct 20Oct 23Oct 25Oct 28Nov 1Nov 4
28°FOct 19Oct 24Oct 27Oct 30Nov 1Nov 3Nov 6Nov 9Nov 14
24°FOct 31Nov 2Nov 5Nov 8Nov 11Nov 13Nov 18Nov 24Dec 1
20°FNov 8Nov 12Nov 16Nov 21Nov 26Dec 1Dec 5Dec 11Dec 23
16°FNov 18Nov 26Dec 2Dec 8Dec 15Dec 22Dec 28Jan 3Jan 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°F186179174170166162158153147
32°F208200195191187183178173166
28°F233225219214210206201196189
24°F265253248243237232227221214
20°F299287280272267261254247237
16°F334322313306299293286278265

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
99% 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
4,126
Cooling degree days, base 65°F
903
Growing degree days, base 40°F
6,327
Growing degree days, base 45°F
4,890
Growing degree days, base 50°F
3,633
Growing degree days, base 55°F
2,556
Growing degree days, base 60°F
1,648

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January862010
February681017
March540072
April2968198
May10955414
June11177616
July1280744
August1252716
September39116528
October26015247
November556154
December774017

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 4.3 km from Macon 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 USC00313228 (Franklin). Public domain.