Etna climate

Etna Frost Dates and Growing Season

NOAA 1991-2020 normals for Corinna, 15.1 km from Etna, elevation 297 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Corinna. 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 May 8 and the first fall freeze around October 3, a growing season of about 148 days.

Median at 36°F
last May 21, first September 23
Median at 32°F
last May 8, first October 3
Median at 28°F
last April 26, first October 15

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°FJun 3May 30May 27May 24May 21May 19May 15May 12May 8
32°FMay 23May 18May 14May 11May 8May 6May 3Apr 30Apr 27
28°FMay 8May 3May 1Apr 29Apr 26Apr 24Apr 21Apr 18Apr 13
24°FApr 25Apr 22Apr 19Apr 16Apr 14Apr 11Apr 8Apr 6Apr 2
20°FApr 17Apr 13Apr 10Apr 7Apr 5Apr 3Apr 2Mar 30Mar 24
16°FApr 9Apr 6Apr 3Apr 1Mar 31Mar 29Mar 26Mar 21Mar 16

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°FSep 10Sep 15Sep 18Sep 21Sep 23Sep 25Sep 28Oct 1Oct 5
32°FSep 21Sep 26Sep 29Oct 1Oct 3Oct 6Oct 9Oct 12Oct 17
28°FOct 1Oct 4Oct 8Oct 12Oct 15Oct 18Oct 22Oct 26Nov 1
24°FOct 13Oct 19Oct 23Oct 27Oct 30Nov 1Nov 4Nov 7Nov 14
20°FOct 29Nov 1Nov 5Nov 8Nov 11Nov 14Nov 17Nov 21Nov 26
16°FNov 8Nov 12Nov 15Nov 19Nov 22Nov 24Nov 27Nov 30Dec 4

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°F142135131128124121117111104
32°F164158155151148144141136129
28°F191184180175171168164159152
24°F216210205200197193189184178
20°F238232226222218214210206200
16°F255249245241237234230225219

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
7,827
Cooling degree days, base 65°F
375
Growing degree days, base 40°F
4,011
Growing degree days, base 45°F
3,009
Growing degree days, base 50°F
2,146
Growing degree days, base 55°F
1,409
Growing degree days, base 60°F
811

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,48500
February1,27800
March1,09702
April672026
May33011181
June9962414
July20151597
August33117549
September19034303
October533168
November85107
December1,24000

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 15.1 km from Etna. 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 USC00171628 (Corinna). Public domain.