Macon County climate

Macon County Frost Dates and Growing Season

NOAA 1991-2020 normals for Lafayette, 2.5 km from Macon County, elevation 975 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Lafayette. 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 3 and the first fall freeze around November 1, a growing season of about 213 days.

Median at 36°F
last April 15, first October 23
Median at 32°F
last April 3, first November 1
Median at 28°F
last March 23, first November 11

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 4Apr 28Apr 22Apr 18Apr 15Apr 11Apr 8Apr 4Mar 31
32°FApr 21Apr 14Apr 9Apr 5Apr 3Mar 31Mar 28Mar 24Mar 18
28°FApr 7Apr 2Mar 30Mar 27Mar 23Mar 20Mar 16Mar 12Mar 5
24°FMar 28Mar 23Mar 19Mar 16Mar 13Mar 8Mar 4Feb 27Feb 21
20°FMar 21Mar 15Mar 11Mar 6Mar 2Feb 27Feb 22Feb 16Feb 8
16°FMar 14Mar 6Mar 1Feb 25Feb 19Feb 13Feb 8Feb 2Jan 25

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 11Oct 16Oct 18Oct 21Oct 23Oct 25Oct 27Oct 30Nov 3
32°FOct 20Oct 24Oct 28Oct 30Nov 1Nov 3Nov 6Nov 10Nov 16
28°FOct 30Nov 2Nov 5Nov 8Nov 11Nov 15Nov 20Nov 25Dec 1
24°FNov 6Nov 11Nov 15Nov 20Nov 24Nov 29Dec 2Dec 6Dec 13
20°FNov 14Nov 21Nov 26Dec 1Dec 5Dec 10Dec 15Dec 21Dec 28
16°FNov 28Dec 3Dec 10Dec 16Dec 22Dec 27Jan 1Jan 6Jan 15

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°F210204199195191187182176167
32°F236228222217213208204199190
28°F261251244239234229224219211
24°F285275269263257253247240231
20°F307297290283278273266258249
16°F332324316308300294288281270

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
3,918
Cooling degree days, base 65°F
1,527
Growing degree days, base 40°F
7,277
Growing degree days, base 45°F
5,840
Growing degree days, base 50°F
4,542
Growing degree days, base 55°F
3,387
Growing degree days, base 60°F
2,381

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January910015
February697029
March5106113
April22835291
May64129530
June4306751
July0420885
August0389854
September22200629
October20137318
November4944100
December788127

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 2.5 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 USC00404987 (Lafayette). Public domain.