Thorsby climate

Thorsby Frost Dates and Growing Season

NOAA 1991-2020 normals for Thorsby Exp Stn, 4.3 km from Thorsby, elevation 680 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Thorsby Exp Stn. 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 21 and the first fall freeze around November 11, a growing season of about 235 days.

Median at 36°F
last April 5, first November 1
Median at 32°F
last March 21, first November 11
Median at 28°F
last March 7, first November 25

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 23Apr 17Apr 13Apr 10Apr 5Apr 2Mar 31Mar 24Mar 17
32°FApr 10Apr 3Mar 30Mar 25Mar 21Mar 17Mar 13Mar 7Feb 28
28°FMar 26Mar 19Mar 15Mar 12Mar 7Mar 3Feb 28Feb 22Feb 15
24°FMar 16Mar 10Mar 4Feb 28Feb 22Feb 16Feb 9Feb 3Jan 28
20°FMar 7Feb 27Feb 18Feb 10Feb 5Jan 31Jan 27Jan 18Jan 7
16°FFeb 23Feb 10Feb 2Jan 31Jan 24Jan 19Jan 13Jan 7Dec 31

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 19Oct 24Oct 27Oct 30Nov 1Nov 3Nov 6Nov 10Nov 15
32°FOct 29Nov 1Nov 5Nov 8Nov 11Nov 15Nov 19Nov 25Dec 1
28°FNov 5Nov 11Nov 16Nov 20Nov 25Nov 30Dec 3Dec 8Dec 21
24°FNov 17Nov 24Dec 1Dec 5Dec 10Dec 16Dec 25Jan 1Jan 10
20°FDec 1Dec 7Dec 15Dec 24Dec 30Jan 2Jan 8Jan 16Jan 30
16°FDec 13Dec 25Jan 1Jan 3Jan 8Jan 13Jan 19Jan 26Feb 6

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°F236226220214210204200195188
32°F263252246241235230225218209
28°F295282275268262257251245234
24°F329317308301293287279271260
20°F363348339332326318307300289
16°F365365365359351343334327314

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
92% of years
16°F or colder
66% 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
2,686
Cooling degree days, base 65°F
1,816
Growing degree days, base 40°F
8,406
Growing degree days, base 45°F
6,776
Growing degree days, base 50°F
5,289
Growing degree days, base 55°F
3,959
Growing degree days, base 60°F
2,795

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January650154
February481177
March32912203
April13845365
May30176611
June1344793
July0442907
August0431896
September6277721
October11477433
November3579162
December580269

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 4.3 km from Thorsby. 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 USC00018209 (Thorsby Exp Stn). Public domain.