Whetstone climate

Whetstone Frost Dates and Growing Season

NOAA 1991-2020 normals for Ft Huachuca Pioneer Airfield, 12.1 km from Whetstone, elevation 4768 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Ft Huachuca Pioneer Airfield. 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 16 and the first fall freeze around November 21, a growing season of about 246 days.

Median at 36°F
last April 9, first November 8
Median at 32°F
last March 16, first November 21
Median at 28°F
last February 20, first December 6

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 26Apr 22Apr 17Apr 12Apr 9Apr 6Apr 1Mar 27Mar 20
32°FApr 12Apr 6Mar 31Mar 23Mar 16Mar 12Mar 7Mar 1Feb 19
28°FMar 23Mar 9Mar 3Feb 27Feb 20Feb 13Feb 7Jan 30Jan 16
24°FFeb 23Feb 14Feb 8Feb 1Jan 26Jan 16Jan 9Jan 3Dec 23
20°FFeb 14Feb 7Jan 29Jan 19Jan 9Jan 5Dec 31Dec 25Dec 15
16°FFeb 16Feb 12Feb 9Feb 1Jan 20Jan 9Jan 4Jan 1Dec 27

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

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°F238228222217211206200194186
32°F277266259252246239232226214
28°F325311302296288282273265252
24°F365355346338331324316308297
20°F365365365365365360350338324
16°F365365365365365365365365357

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
89% of years
20°F or colder
46% of years
16°F or colder
11% 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
2,414
Cooling degree days, base 65°F
1,615
Growing degree days, base 40°F
8,373
Growing degree days, base 45°F
6,652
Growing degree days, base 50°F
5,082
Growing degree days, base 55°F
3,715
Growing degree days, base 60°F
2,563

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January546043
February426179
March3133181
April14222334
May42144568
June0376826
July0406871
August0355820
September2239687
October7766457
November3144172
December553044

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 12.1 km from Whetstone. 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 USW00053146 (Ft Huachuca Pioneer Airfield). Public domain.