Tucson Estates climate

Tucson Estates Frost Dates and Growing Season

NOAA 1991-2020 normals for Tucson U Of A #1, 11.2 km from Tucson Estates, elevation 2315 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Tucson U Of A #1. 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 February 11 and the first fall freeze around December 2, a growing season of about 293 days.

Median at 36°F
last March 6, first November 22
Median at 32°F
last February 11, first December 2
Median at 28°F
last January 18, first December 15

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°FMar 30Mar 22Mar 16Mar 10Mar 6Mar 2Feb 25Feb 20Feb 12
32°FMar 7Feb 28Feb 22Feb 16Feb 11Feb 6Feb 2Jan 27Jan 16
28°FFeb 17Feb 8Feb 2Jan 27Jan 18Jan 11Jan 5Dec 30Dec 21
24°FFeb 4Jan 19Jan 11Jan 4Dec 31Dec 26Dec 22Dec 14Dec 7
20°F–––––––––
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°FNov 4Nov 11Nov 16Nov 18Nov 22Nov 24Nov 27Dec 1Dec 6
32°FNov 16Nov 22Nov 26Nov 29Dec 2Dec 5Dec 8Dec 13Dec 20
28°FNov 29Dec 3Dec 8Dec 11Dec 15Dec 21Dec 26Jan 2Jan 17
24°FDec 6Dec 11Dec 15Dec 21Dec 25Dec 29Jan 3Jan 11Jan 29
20°F–––––––––
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°F285275268262257252245237228
32°F326315306299293287281273263
28°F365356348341336330322312299
24°F365365365365365365361350337
20°F365365365365365365365365365
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
91% of years
24°F or colder
38% of years
20°F or colder
2% of years
16°F or colder
0% 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
1,363
Cooling degree days, base 65°F
3,328
Growing degree days, base 40°F
11,093
Growing degree days, base 45°F
9,283
Growing degree days, base 50°F
7,536
Growing degree days, base 55°F
5,929
Growing degree days, base 60°F
4,524

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January3651134
February2524184
March14136363
April45126531
May4348809
June06091,059
July07211,186
August06801,145
September0528978
October19239685
November16136333
December3771129

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 11.2 km from Tucson Estates. 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 USC00028817 (Tucson U Of A #1). Public domain.