Thermal climate

Thermal Frost Dates and Growing Season

NOAA 1991-2020 normals for Desert Resorts Rgnl AP, 2.4 km from Thermal, elevation -118 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Desert Resorts Rgnl AP. 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 7 and the first fall freeze around December 2, a growing season of about 298 days.

Median at 36°F
last February 28, first November 21
Median at 32°F
last February 7, first December 2
Median at 28°F
last January 15, first December 13

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 25Mar 12Mar 8Mar 3Feb 28Feb 24Feb 19Feb 12Feb 1
32°FMar 1Feb 23Feb 17Feb 13Feb 7Feb 1Jan 27Jan 19Jan 7
28°FFeb 16Feb 6Jan 31Jan 22Jan 15Jan 7Jan 2Dec 27Dec 18
24°FFeb 1Jan 20Jan 9Jan 3Dec 31Dec 26Dec 21Dec 16Dec 9
20°FJan 20Jan 7Jan 2Dec 31Dec 27Dec 22Dec 17Dec 12Dec 6
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 5Nov 10Nov 15Nov 17Nov 21Nov 24Nov 27Dec 1Dec 5
32°FNov 16Nov 22Nov 26Nov 30Dec 2Dec 5Dec 9Dec 14Dec 21
28°FNov 24Dec 1Dec 5Dec 10Dec 13Dec 17Dec 22Dec 28Jan 5
24°FDec 1Dec 8Dec 13Dec 17Dec 21Dec 25Dec 29Jan 3Jan 16
20°FDec 6Dec 11Dec 16Dec 22Dec 26Dec 31Jan 2Jan 7Jan 20
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°F295283277272266260254247236
32°F331319310303298291285278269
28°F362353346340334327320310297
24°F365365365365364357350341329
20°F365365365365365365365365358
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
88% of years
24°F or colder
51% of years
20°F or colder
14% 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
1,108
Cooling degree days, base 65°F
3,880
Growing degree days, base 40°F
11,897
Growing degree days, base 45°F
10,078
Growing degree days, base 50°F
8,296
Growing degree days, base 55°F
6,629
Growing degree days, base 60°F
5,155

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January3122171
February19111246
March7879467
April18198630
May2428891
June06321,082
July08141,279
August07921,257
September05961,046
October9285741
November14142355
December3571132

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 2.4 km from Thermal. 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 USW00003104 (Desert Resorts Rgnl AP). Public domain.