Oro Valley climate

Oro Valley Frost Dates and Growing Season

NOAA 1991-2020 normals for Catalina SP, 4.5 km from Oro Valley, elevation 2707 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Catalina SP. 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 2 and the first fall freeze around November 11, a growing season of about 222 days.

Median at 36°F
last April 18, first November 1
Median at 32°F
last April 2, first November 11
Median at 28°F
last March 12, 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 5Apr 30Apr 25Apr 21Apr 18Apr 15Apr 11Apr 8Apr 4
32°FApr 18Apr 12Apr 8Apr 5Apr 2Mar 31Mar 26Mar 21Mar 16
28°FApr 1Mar 27Mar 21Mar 16Mar 12Mar 9Mar 5Mar 2Feb 22
24°FMar 12Mar 7Mar 3Feb 27Feb 21Feb 15Feb 10Feb 4Jan 24
20°FFeb 26Feb 16Feb 8Feb 2Jan 27Jan 19Jan 10Jan 2Dec 21
16°FFeb 14Feb 3Jan 26Jan 17Jan 10Jan 2Dec 29Dec 19Dec 4

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 18Oct 23Oct 27Oct 29Nov 1Nov 4Nov 7Nov 11Nov 17
32°FOct 26Oct 31Nov 4Nov 7Nov 11Nov 15Nov 18Nov 23Nov 29
28°FNov 3Nov 9Nov 14Nov 18Nov 21Nov 25Nov 30Dec 4Dec 10
24°FNov 13Nov 20Nov 25Nov 29Dec 4Dec 9Dec 12Dec 17Dec 25
20°FNov 24Dec 1Dec 8Dec 14Dec 19Dec 26Jan 2Jan 16Jan 29
16°FNov 28Dec 11Dec 22Dec 29Jan 2Jan 9Jan 18Jan 31Feb 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°F218210205200195191187181173
32°F245238232227222217211205196
28°F278270264257252246241234226
24°F319307299292286279273266256
20°F365350343334328322314305292
16°F365365365365365365356344330

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
86% of years
16°F or colder
34% 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
2,180
Cooling degree days, base 65°F
2,445
Growing degree days, base 40°F
9,419
Growing degree days, base 45°F
7,671
Growing degree days, base 50°F
6,057
Growing degree days, base 55°F
4,647
Growing degree days, base 60°F
3,452

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January502052
February419077
March2943195
April12242374
May23198640
June0455904
July06261,091
August05741,038
September1410859
October53129543
November2609225
December507059

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 4.5 km from Oro Valley. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00021357 (Catalina SP). Public domain.