Hemet climate

Hemet Frost Dates and Growing Season

NOAA 1991-2020 normals for San Jacinto, 5.4 km from Hemet, elevation 1525 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for San Jacinto. 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 January 31 and the first fall freeze around December 10, a growing season of about 315 days.

Median at 36°F
last March 5, first November 24
Median at 32°F
last January 31, first December 10
Median at 28°F
last January 3, first December 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°FApr 8Mar 29Mar 20Mar 12Mar 5Feb 28Feb 23Feb 17Feb 6
32°FFeb 28Feb 21Feb 14Feb 6Jan 31Jan 25Jan 17Jan 6Dec 31
28°FJan 29Jan 21Jan 12Jan 7Jan 3Dec 31Dec 25Dec 19Dec 11
24°FJan 14Jan 8Jan 5Jan 3Jan 1Dec 30Dec 24Dec 17Dec 10
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 5Nov 12Nov 17Nov 21Nov 24Nov 28Dec 2Dec 6Dec 12
32°FNov 22Nov 29Dec 2Dec 6Dec 10Dec 14Dec 18Dec 26Jan 6
28°FDec 2Dec 8Dec 13Dec 17Dec 21Dec 26Dec 30Jan 4Jan 15
24°FDec 9Dec 16Dec 23Dec 27Dec 31Jan 1Jan 4Jan 7Jan 12
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°F297281275268260252244234223
32°F348339332324315306297287274
28°F365365365365359353346340330
24°F365365365365365365365365365
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
97% of years
28°F or colder
59% of years
24°F or colder
11% of years
20°F or colder
0% 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
1,801
Cooling degree days, base 65°F
1,810
Growing degree days, base 40°F
9,135
Growing degree days, base 45°F
7,326
Growing degree days, base 50°F
5,606
Growing degree days, base 55°F
4,076
Growing degree days, base 60°F
2,810

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January3740124
February3161131
March2389245
April14530339
May57115523
June7252695
July0445910
August0477942
September3340787
October47124543
November21117265
December4030103

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 5.4 km from Hemet. 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 USC00047813 (San Jacinto). Public domain.