Alcoa climate

Alcoa Frost Dates and Growing Season

NOAA 1991-2020 normals for Knoxville Mcghee Tyson AP, 3.3 km from Alcoa, elevation 962 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Knoxville Mcghee Tyson AP. 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 1 and the first fall freeze around November 2, a growing season of about 215 days.

Median at 36°F
last April 14, first October 24
Median at 32°F
last April 1, first November 2
Median at 28°F
last March 19, first November 13

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 2Apr 26Apr 22Apr 18Apr 14Apr 11Apr 7Apr 3Mar 27
32°FApr 17Apr 12Apr 7Apr 4Apr 1Mar 29Mar 24Mar 19Mar 14
28°FApr 5Apr 1Mar 28Mar 24Mar 19Mar 16Mar 12Mar 6Feb 28
24°FMar 27Mar 19Mar 15Mar 11Mar 6Mar 2Feb 26Feb 21Feb 12
20°FMar 16Mar 9Mar 3Feb 26Feb 20Feb 15Feb 7Feb 1Jan 22
16°FMar 4Feb 25Feb 15Feb 7Feb 1Jan 29Jan 23Jan 16Jan 6

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 12Oct 16Oct 20Oct 22Oct 24Oct 26Oct 30Nov 1Nov 5
32°FOct 21Oct 25Oct 28Oct 31Nov 2Nov 4Nov 7Nov 10Nov 15
28°FNov 1Nov 4Nov 7Nov 10Nov 13Nov 16Nov 20Nov 23Dec 1
24°FNov 11Nov 15Nov 19Nov 23Nov 27Dec 1Dec 4Dec 11Dec 22
20°FNov 23Nov 30Dec 4Dec 9Dec 16Dec 22Dec 29Jan 2Jan 9
16°FDec 6Dec 15Dec 23Dec 29Jan 2Jan 6Jan 12Jan 17Jan 27

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°F212205200195191187182177170
32°F236228223219215211206200194
28°F262254249243239235230225217
24°F295284278272265260255248239
20°F330320311303297290283276264
16°F360348339333328322313304292

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
99% 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
3,528
Cooling degree days, base 65°F
1,574
Growing degree days, base 40°F
7,505
Growing degree days, base 45°F
6,007
Growing degree days, base 50°F
4,664
Growing degree days, base 55°F
3,481
Growing degree days, base 60°F
2,453

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January803023
February618036
March4525130
April19836306
May53143556
June2311759
July0420885
August0392857
September17221654
October18842334
November482393
December716032

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 3.3 km from Alcoa. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USW00013891 (Knoxville Mcghee Tyson AP). Public domain.