Cottonwood climate

Cottonwood Frost Dates and Growing Season

NOAA 1991-2020 normals for Cottonwood 2 Wsw, 3.7 km from Cottonwood, elevation 3945 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Cottonwood 2 Wsw. 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 6 and the first fall freeze around October 13, a growing season of about 156 days.

Median at 36°F
last May 31, first October 1
Median at 32°F
last May 6, first October 13
Median at 28°F
last April 21, first October 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°FJun 20Jun 13Jun 9Jun 4May 31May 26May 22May 16May 10
32°FMay 26May 19May 15May 10May 6May 3Apr 30Apr 27Apr 22
28°FMay 10May 2Apr 29Apr 25Apr 21Apr 17Apr 13Apr 9Apr 1
24°FApr 19Apr 11Apr 6Apr 2Mar 30Mar 26Mar 21Mar 15Mar 8
20°FMar 28Mar 22Mar 16Mar 11Mar 7Mar 3Feb 28Feb 22Feb 14
16°FMar 12Mar 5Feb 28Feb 25Feb 21Feb 16Feb 11Feb 5Jan 24

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 12Sep 19Sep 24Sep 27Oct 1Oct 3Oct 5Oct 9Oct 14
32°FSep 28Oct 3Oct 6Oct 9Oct 13Oct 15Oct 18Oct 22Oct 27
28°FOct 9Oct 15Oct 18Oct 21Oct 24Oct 28Oct 31Nov 5Nov 12
24°FOct 18Oct 23Oct 28Nov 1Nov 5Nov 10Nov 13Nov 17Nov 22
20°FOct 25Nov 2Nov 9Nov 13Nov 16Nov 20Nov 23Nov 27Dec 4
16°FNov 3Nov 12Nov 18Nov 23Nov 26Dec 1Dec 6Dec 10Dec 18

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°F14513613012311911510810392
32°F181172166160156151146140132
28°F211203197192188183178171161
24°F246236231225220215208201192
20°F282273265258251245239232223
16°F316305295288281274266257246

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
6,718
Cooling degree days, base 65°F
393
Growing degree days, base 40°F
3,935
Growing degree days, base 45°F
2,875
Growing degree days, base 50°F
2,010
Growing degree days, base 55°F
1,317
Growing degree days, base 60°F
781

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,05700
February88900
March80504
April615031
May3906142
June21528274
July51155569
August43156578
September18447326
October528379
November84706
December1,09400

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 3.7 km from Cottonwood. 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 USC00102159 (Cottonwood 2 Wsw). Public domain.