Sierra Vista climate

Sierra Vista Frost Dates and Growing Season

NOAA 1991-2020 normals for Sierra Vista, 3 km from Sierra Vista, elevation 4606 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Sierra Vista. 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 5 and the first fall freeze around November 9, a growing season of about 216 days.

Median at 36°F
last April 20, first October 30
Median at 32°F
last April 5, first November 9
Median at 28°F
last March 15, first November 21

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 4Apr 30Apr 27Apr 23Apr 20Apr 16Apr 13Apr 9Apr 5
32°FApr 21Apr 15Apr 11Apr 8Apr 5Apr 2Mar 30Mar 24Mar 15
28°FApr 5Mar 31Mar 25Mar 20Mar 15Mar 10Mar 7Feb 28Feb 21
24°FMar 15Mar 6Mar 1Feb 24Feb 19Feb 14Feb 7Jan 31Jan 20
20°FFeb 20Feb 12Feb 5Jan 31Jan 24Jan 15Jan 9Jan 3Dec 25
16°FFeb 8Feb 2Jan 25Jan 17Jan 9Jan 4Dec 31Dec 24Dec 15

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 15Oct 20Oct 24Oct 27Oct 30Nov 1Nov 4Nov 7Nov 12
32°FOct 23Oct 29Nov 2Nov 5Nov 9Nov 12Nov 15Nov 18Nov 23
28°FNov 4Nov 10Nov 15Nov 18Nov 21Nov 24Nov 27Dec 1Dec 5
24°FNov 16Nov 22Nov 26Nov 30Dec 3Dec 6Dec 10Dec 15Dec 21
20°FNov 28Dec 4Dec 10Dec 15Dec 20Dec 24Dec 29Jan 4Jan 17
16°FDec 7Dec 16Dec 23Dec 28Jan 1Jan 4Jan 10Jan 22Feb 3

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°F211204199195191187183178171
32°F239231226221216212207202194
28°F276267260254248241235228220
24°F323311302294287281273266256
20°F361352344336329322314305294
16°F365365365365365361353342331

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
93% of years
16°F or colder
48% 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
2,666
Cooling degree days, base 65°F
1,450
Growing degree days, base 40°F
7,969
Growing degree days, base 45°F
6,282
Growing degree days, base 50°F
4,768
Growing degree days, base 55°F
3,463
Growing degree days, base 60°F
2,359

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January608022
February462052
March3421160
April16115309
May42126549
June1353802
July0372837
August0326790
September4207652
October9449423
November3502147
December603023

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 km from Sierra Vista. 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 USC00027880 (Sierra Vista). Public domain.