Sells climate

Sells Frost Dates and Growing Season

NOAA 1991-2020 normals for Kitt Peak, 27.3 km from Sells, elevation 6790 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Kitt Peak. 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 26 and the first fall freeze around November 4, a growing season of about 195 days.

Median at 36°F
last May 7, first October 26
Median at 32°F
last April 26, first November 4
Median at 28°F
last April 7, first November 17

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 29May 20May 16May 12May 7May 4Apr 30Apr 26Apr 18
32°FMay 17May 9May 4Apr 30Apr 26Apr 21Apr 15Apr 9Apr 1
28°FMay 5Apr 27Apr 21Apr 14Apr 7Apr 1Mar 28Mar 21Mar 8
24°FApr 23Apr 9Mar 31Mar 25Mar 17Mar 9Mar 2Feb 22Feb 10
20°FMar 31Mar 14Mar 3Feb 25Feb 17Feb 7Jan 29Jan 17Jan 3
16°FFeb 27Feb 16Feb 7Jan 31Jan 23Jan 14Jan 7Dec 31Dec 18

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 10Oct 16Oct 20Oct 23Oct 26Oct 30Nov 3Nov 7Nov 13
32°FOct 18Oct 24Oct 28Nov 1Nov 4Nov 8Nov 13Nov 17Nov 24
28°FOct 27Nov 3Nov 7Nov 13Nov 17Nov 22Nov 27Dec 2Dec 8
24°FNov 9Nov 17Nov 24Nov 29Dec 3Dec 7Dec 12Dec 17Dec 25
20°FNov 23Dec 1Dec 8Dec 13Dec 18Dec 24Dec 31Jan 8Jan 29
16°FDec 3Dec 12Dec 19Dec 28Jan 2Jan 8Jan 16Jan 30Feb 10

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°F198190183178171166161155146
32°F225214208202195190182176165
28°F257245237230223216209202190
24°F300285275267258250243234223
20°F349335323310300291281270257
16°F365365365358348339330319303

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
96% of years
16°F or colder
69% 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
3,992
Cooling degree days, base 65°F
616
Growing degree days, base 40°F
6,040
Growing degree days, base 45°F
4,542
Growing degree days, base 50°F
3,241
Growing degree days, base 55°F
2,158
Growing degree days, base 60°F
1,283

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January710016
February626022
March570059
April3862135
May19433321
June26161585
July9178634
August12142595
September4785489
October22715274
November473092
December713020

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 27.3 km from Sells. 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 USC00024675 (Kitt Peak). Public domain.