Arivaca climate

Arivaca Frost Dates and Growing Season

NOAA 1991-2020 normals for Sasabe, 22.5 km from Arivaca, elevation 3590 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Sasabe. 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 21 and the first fall freeze around November 20, a growing season of about 246 days.

Median at 36°F
last April 14, first November 8
Median at 32°F
last March 21, first November 20
Median at 28°F
last February 20, first December 3

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 3Apr 27Apr 22Apr 18Apr 14Apr 9Apr 6Apr 1Mar 25
32°FApr 14Apr 5Mar 31Mar 27Mar 21Mar 14Mar 7Mar 2Feb 23
28°FMar 19Mar 9Mar 3Feb 26Feb 20Feb 13Feb 5Jan 29Jan 15
24°FFeb 23Feb 13Feb 5Jan 29Jan 18Jan 8Jan 1Dec 26Dec 15
20°FFeb 9Feb 3Jan 26Jan 15Jan 8Jan 2Dec 29Dec 20Dec 11
16°F–––––––––

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 15Nov 19Nov 24
32°FNov 1Nov 7Nov 13Nov 16Nov 20Nov 24Nov 28Dec 2Dec 7
28°FNov 14Nov 21Nov 26Nov 30Dec 3Dec 6Dec 11Dec 17Dec 23
24°FNov 28Dec 4Dec 9Dec 14Dec 19Dec 25Dec 30Jan 6Jan 27
20°FDec 7Dec 15Dec 23Dec 30Jan 3Jan 7Jan 19Jan 31Feb 6
16°F–––––––––

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°F235225218213207202196190182
32°F277266259252246240232225215
28°F327312303295288281274266255
24°F365359350343335328320309297
20°F365365365365365365365351333
16°F365365365365365365365365365

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
85% of years
20°F or colder
32% of years
16°F or colder
3% 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
1,986
Cooling degree days, base 65°F
2,063
Growing degree days, base 40°F
9,218
Growing degree days, base 45°F
7,453
Growing degree days, base 50°F
5,798
Growing degree days, base 55°F
4,327
Growing degree days, base 60°F
3,083

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January445088
February3660107
March2678229
April12737363
May34164595
June1412861
July0513978
August0460925
September1335785
October48120537
November23114251
December467080

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 22.5 km from Arivaca. 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 USC00027619 (Sasabe). Public domain.