Sequatchie County climate

Sequatchie County Frost Dates and Growing Season

NOAA 1991-2020 normals for Whitwell-Sequatchie Vly, 10.7 km from Sequatchie County, elevation 1020 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Whitwell-Sequatchie Vly. 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 26 and the first fall freeze around November 8, a growing season of about 228 days.

Median at 36°F
last April 9, first October 28
Median at 32°F
last March 26, first November 8
Median at 28°F
last March 12, first November 24

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 27Apr 21Apr 17Apr 12Apr 9Apr 5Apr 1Mar 28Mar 21
32°FApr 13Apr 7Apr 3Mar 31Mar 26Mar 22Mar 18Mar 13Mar 6
28°FApr 2Mar 26Mar 20Mar 16Mar 12Mar 7Mar 2Feb 27Feb 18
24°FMar 21Mar 13Mar 7Mar 3Feb 28Feb 22Feb 17Feb 11Feb 3
20°FMar 10Mar 2Feb 24Feb 17Feb 12Feb 6Feb 1Jan 27Jan 17
16°FFeb 28Feb 17Feb 9Feb 3Jan 31Jan 26Jan 20Jan 12Jan 3

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 16Oct 20Oct 23Oct 26Oct 28Oct 31Nov 3Nov 7Nov 12
32°FOct 25Oct 30Nov 1Nov 5Nov 8Nov 12Nov 16Nov 21Nov 29
28°FNov 4Nov 10Nov 16Nov 19Nov 24Nov 29Dec 2Dec 6Dec 13
24°FNov 19Nov 25Dec 1Dec 4Dec 8Dec 13Dec 20Dec 26Jan 1
20°FDec 1Dec 8Dec 14Dec 22Dec 27Jan 1Jan 5Jan 12Jan 21
16°FDec 12Dec 21Dec 28Jan 1Jan 6Jan 11Jan 16Jan 23Feb 1

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°F225217210206201196191186178
32°F254244238233228223217211203
28°F284274267261256250245237229
24°F316305298291285278271264255
20°F343333326319311306300291281
16°F365360350342335331325314303

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
98% of years
16°F or colder
85% 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
3,276
Cooling degree days, base 65°F
1,554
Growing degree days, base 40°F
7,693
Growing degree days, base 45°F
6,156
Growing degree days, base 50°F
4,762
Growing degree days, base 55°F
3,519
Growing degree days, base 60°F
2,454

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January766034
February582149
March40710156
April18344329
May58134542
June2287735
July0395860
August0388852
September16240673
October16850361
November4205123
December673147

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 10.7 km from Sequatchie 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 USC00409691 (Whitwell-Sequatchie Vly). Public domain.