Descanso climate

Descanso Frost Dates and Growing Season

NOAA 1991-2020 normals for Cuyamaca, 15.4 km from Descanso, elevation 4640 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Cuyamaca. 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 19 and the first fall freeze around October 27, a growing season of about 190 days.

Median at 36°F
last May 13, first October 12
Median at 32°F
last April 19, first October 27
Median at 28°F
last March 14, first November 12

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°FJun 6Jun 1May 26May 18May 13May 8May 2Apr 28Apr 22
32°FMay 14May 3Apr 29Apr 24Apr 19Apr 14Apr 8Apr 2Mar 24
28°FApr 13Apr 5Mar 29Mar 21Mar 14Mar 8Mar 1Feb 24Feb 14
24°FMar 12Mar 2Feb 25Feb 20Feb 14Feb 8Feb 1Jan 25Jan 10
20°FFeb 24Feb 16Feb 6Jan 30Jan 20Jan 10Jan 4Dec 27Dec 14
16°FFeb 18Feb 3Jan 27Jan 17Jan 7Jan 4Dec 29Dec 15Dec 7

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°FSep 28Oct 1Oct 5Oct 8Oct 12Oct 15Oct 18Oct 22Oct 29
32°FOct 9Oct 15Oct 19Oct 23Oct 27Oct 31Nov 3Nov 7Nov 13
28°FOct 21Oct 29Nov 3Nov 8Nov 12Nov 16Nov 22Nov 27Dec 4
24°FNov 9Nov 17Nov 24Dec 1Dec 4Dec 9Dec 14Dec 20Jan 1
20°FNov 27Dec 2Dec 9Dec 16Dec 24Jan 1Jan 6Jan 20Feb 3
16°FDec 3Dec 11Dec 23Dec 30Jan 4Jan 10Jan 21Jan 29Feb 13

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°F179170162156150144137131123
32°F224212204197190184178170156
28°F278265254246239231222212198
24°F335321311303294287278268253
20°F365365359351342334326317305
16°F365365365365365365365352337

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
79% of years
16°F or colder
30% 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
4,519
Cooling degree days, base 65°F
537
Growing degree days, base 40°F
5,372
Growing degree days, base 45°F
3,921
Growing degree days, base 50°F
2,729
Growing degree days, base 55°F
1,795
Growing degree days, base 60°F
1,077

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January71208
February634012
March598034
April477074
May3119204
June10765413
July15190640
August9190646
September7478457
October3084191
November540045
December73506

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 15.4 km from Descanso. 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 USC00042239 (Cuyamaca). Public domain.