Tumbling Shoals climate

Tumbling Shoals Frost Dates and Growing Season

NOAA 1991-2020 normals for Greers Ferry Dam, 3.8 km from Tumbling Shoals, elevation 527 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Greers Ferry Dam. 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 31 and the first fall freeze around November 6, a growing season of about 222 days.

Median at 36°F
last April 11, first October 28
Median at 32°F
last March 31, first November 6
Median at 28°F
last March 16, first November 19

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 28Apr 22Apr 18Apr 14Apr 11Apr 8Apr 5Apr 2Mar 28
32°FApr 16Apr 9Apr 5Apr 2Mar 31Mar 27Mar 23Mar 18Mar 11
28°FApr 2Mar 29Mar 23Mar 19Mar 16Mar 12Mar 8Mar 3Feb 28
24°FMar 20Mar 15Mar 11Mar 7Mar 3Mar 1Feb 26Feb 21Feb 14
20°FMar 12Mar 5Mar 1Feb 26Feb 22Feb 17Feb 12Feb 5Jan 29
16°FMar 2Feb 23Feb 16Feb 10Feb 4Feb 1Jan 28Jan 20Jan 9

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 25Oct 28Oct 30Nov 1Nov 4Nov 10
32°FOct 26Oct 30Nov 1Nov 4Nov 6Nov 10Nov 14Nov 19Nov 24
28°FNov 3Nov 7Nov 11Nov 15Nov 19Nov 22Nov 26Dec 1Dec 6
24°FNov 12Nov 17Nov 22Nov 26Nov 30Dec 4Dec 8Dec 14Dec 24
20°FNov 23Nov 30Dec 5Dec 12Dec 18Dec 24Dec 29Jan 4Jan 12
16°FDec 3Dec 14Dec 23Dec 28Jan 1Jan 5Jan 9Jan 16Jan 28

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°F218212208204200195191185179
32°F246238233227222217213207200
28°F272265258252247243238233224
24°F299289283277271266260254246
20°F328317309304299293286278266
16°F358345337331324317309303294

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
94% 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
3,577
Cooling degree days, base 65°F
1,725
Growing degree days, base 40°F
7,645
Growing degree days, base 45°F
6,158
Growing degree days, base 50°F
4,824
Growing degree days, base 55°F
3,640
Growing degree days, base 60°F
2,607

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January836017
February639033
March4676121
April20035304
May48139557
June2333781
July0471936
August0444908
September16238672
October17153359
November4575111
December743026

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 3.8 km from Tumbling Shoals. 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 USC00032978 (Greers Ferry Dam). Public domain.