Morongo Valley climate

Morongo Valley Frost Dates and Growing Season

NOAA 1991-2020 normals for Morongo Valley N, 4.7 km from Morongo Valley, elevation 3145 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Morongo Valley N. 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 25 and the first fall freeze around December 15, a growing season of about 297 days.

Median at 36°F
last March 31, first December 1
Median at 32°F
last February 25, first December 15
Median at 28°F
last January 25, first January 6

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 29Apr 19Apr 12Apr 7Mar 31Mar 24Mar 16Mar 7Feb 20
32°FApr 3Mar 22Mar 11Mar 2Feb 25Feb 14Feb 3Jan 21Jan 7
28°FFeb 28Feb 22Feb 14Feb 1Jan 25Jan 16Jan 8Jan 1Dec 20
24°FJan 31Jan 26Jan 22Jan 17Jan 14Jan 12Jan 10Jan 6Jan 3
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 7Nov 16Nov 22Nov 28Dec 1Dec 5Dec 9Dec 12Dec 16
32°FNov 23Dec 1Dec 7Dec 11Dec 15Dec 19Dec 24Jan 1Jan 16
28°FDec 8Dec 17Dec 25Dec 30Jan 6Jan 12Jan 21Jan 30Feb 14
24°FJan 2Jan 5Jan 9Jan 11Jan 13Jan 15Jan 20Jan 24Jan 30
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°F287271260252244238231222208
32°F343329317307297286275265250
28°F365365365361352343333318306
24°F365365365365365365365365362
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
98% of years
28°F or colder
64% of years
24°F or colder
14% 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
2,217
Cooling degree days, base 65°F
2,077
Growing degree days, base 40°F
9,006
Growing degree days, base 45°F
7,272
Growing degree days, base 50°F
5,671
Growing degree days, base 55°F
4,250
Growing degree days, base 60°F
3,053

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January465087
February3881116
March2986208
April17933315
May80146531
June6337781
July0501966
August0533998
September6365810
October59135542
November25720239
December480079

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 4.7 km from Morongo Valley. 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 USC00045860 (Morongo Valley N). Public domain.