Willcox climate

Willcox Frost Dates and Growing Season

NOAA 1991-2020 normals for Willcox, 0.5 km from Willcox, elevation 4170 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Willcox. 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 9 and the first fall freeze around October 31, a growing season of about 204 days.

Median at 36°F
last April 26, first October 22
Median at 32°F
last April 9, first October 31
Median at 28°F
last March 16, first November 12

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 10May 5May 2Apr 29Apr 26Apr 22Apr 19Apr 15Apr 9
32°FApr 29Apr 21Apr 16Apr 12Apr 9Apr 5Mar 31Mar 28Mar 20
28°FApr 10Apr 2Mar 27Mar 21Mar 16Mar 13Mar 8Mar 3Feb 24
24°FMar 13Mar 8Mar 3Feb 28Feb 24Feb 18Feb 12Feb 6Jan 30
20°FFeb 26Feb 18Feb 11Feb 6Feb 1Jan 29Jan 23Jan 16Jan 5
16°FFeb 10Feb 1Jan 28Jan 22Jan 17Jan 11Jan 3Dec 27Dec 14

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 11Oct 15Oct 18Oct 20Oct 22Oct 24Oct 27Oct 29Nov 3
32°FOct 20Oct 23Oct 26Oct 29Oct 31Nov 3Nov 6Nov 10Nov 14
28°FOct 28Nov 1Nov 5Nov 9Nov 12Nov 15Nov 18Nov 22Nov 26
24°FNov 8Nov 14Nov 18Nov 21Nov 25Nov 29Dec 2Dec 5Dec 11
20°FNov 21Nov 26Nov 30Dec 4Dec 8Dec 13Dec 19Dec 25Jan 3
16°FDec 1Dec 8Dec 15Dec 23Dec 29Jan 3Jan 9Jan 16Jan 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°F198191186182178175170166159
32°F225220214209204199194189181
28°F264254248243237232225218209
24°F303293285279274268262257246
20°F343332325317311306299291281
16°F365365365358348342335329316

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
98% of years
16°F or colder
72% 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
2,758
Cooling degree days, base 65°F
1,787
Growing degree days, base 40°F
8,211
Growing degree days, base 45°F
6,534
Growing degree days, base 50°F
5,044
Growing degree days, base 55°F
3,771
Growing degree days, base 60°F
2,691

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January625013
February466043
March3401155
April16419310
May35142572
June1382831
July0490955
August0437902
September3269715
October10048415
November3791122
December645012

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 0.5 km from Willcox. 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 USC00029334 (Willcox). Public domain.