McMinn County climate

McMinn County Frost Dates and Growing Season

NOAA 1991-2020 normals for Athens, 3.2 km from McMinn County, elevation 940 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Athens. 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 6 and the first fall freeze around October 31, a growing season of about 208 days.

Median at 36°F
last April 20, first October 23
Median at 32°F
last April 6, first October 31
Median at 28°F
last March 27, first November 10

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 5Apr 30Apr 27Apr 24Apr 20Apr 16Apr 12Apr 8Apr 4
32°FApr 24Apr 18Apr 14Apr 9Apr 6Apr 3Mar 31Mar 27Mar 20
28°FApr 10Apr 6Apr 2Mar 30Mar 27Mar 22Mar 18Mar 13Mar 6
24°FApr 1Mar 26Mar 20Mar 16Mar 12Mar 7Mar 3Feb 27Feb 18
20°FMar 19Mar 12Mar 6Mar 1Feb 25Feb 19Feb 12Feb 5Jan 29
16°FMar 7Feb 28Feb 20Feb 13Feb 6Feb 1Jan 28Jan 20Jan 10

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 10Oct 15Oct 18Oct 20Oct 23Oct 25Oct 27Oct 31Nov 3
32°FOct 20Oct 24Oct 26Oct 29Oct 31Nov 2Nov 5Nov 8Nov 13
28°FOct 30Nov 1Nov 4Nov 7Nov 10Nov 13Nov 17Nov 22Nov 29
24°FNov 6Nov 11Nov 15Nov 19Nov 24Nov 29Dec 1Dec 6Dec 18
20°FNov 16Nov 25Dec 1Dec 3Dec 8Dec 14Dec 22Dec 28Jan 5
16°FDec 1Dec 8Dec 18Dec 26Dec 31Jan 3Jan 9Jan 15Jan 25

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°F206200195190186182177172165
32°F228221216211208203200195187
28°F255246240235230226220214208
24°F288278271263257251245239231
20°F322311301295289281276268256
16°F353339332326317309303293281

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
95% 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
3,700
Cooling degree days, base 65°F
1,479
Growing degree days, base 40°F
7,288
Growing degree days, base 45°F
5,813
Growing degree days, base 50°F
4,495
Growing degree days, base 55°F
3,336
Growing degree days, base 60°F
2,333

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January825022
February646030
March4854113
April22928276
May67123522
June4286732
July0402866
August0378843
September19214645
October19840325
November496389
December731133

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 3.2 km from McMinn 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 USC00400284 (Athens). Public domain.