Escondido Frost Dates and Growing Season

NOAA 1991-2020 normals for Escondido #2, 0.4 km from Escondido, elevation 600 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Escondido #2. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

A freeze (32°F or colder) happens in only 39 percent of years at Escondido #2, so there is no typical freeze season.

Median at 36°F: last January 31, first December 18
Median at 32°F: last January 2, first December 30

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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	Mar 1	Feb 21	Feb 13	Feb 5	Jan 31	Jan 21	Jan 13	Jan 5	Dec 29
32°F	Feb 4	Jan 25	Jan 14	Jan 7	Jan 2	Dec 31	Dec 28	Dec 22	Dec 14
28°F	–	–	–	–	–	–	–	–	–
24°F	–	–	–	–	–	–	–	–	–
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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	Nov 27	Dec 4	Dec 10	Dec 14	Dec 18	Dec 22	Dec 26	Jan 1	Jan 19
32°F	Dec 8	Dec 15	Dec 23	Dec 27	Dec 30	Jan 1	Jan 7	Jan 14	Jan 29
28°F	–	–	–	–	–	–	–	–	–
24°F	–	–	–	–	–	–	–	–	–
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.

Threshold	10%	20%	30%	40%	50%	60%	70%	80%	90%
36°F	356	347	339	332	324	315	308	297	284
32°F	365	365	365	365	365	365	360	350	339
28°F	365	365	365	365	365	365	365	365	365
24°F	365	365	365	365	365	365	365	365	365
20°F	365	365	365	365	365	365	365	365	365
16°F	365	365	365	365	365	365	365	365	365

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder: 94% of years
32°F or colder: 39% of years
28°F or colder: 3% of years
24°F or colder: 0% 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: 1,214
Cooling degree days, base 65°F: 1,517
Growing degree days, base 40°F: 9,429
Growing degree days, base 45°F: 7,604
Growing degree days, base 50°F: 5,796
Growing degree days, base 55°F: 4,091
Growing degree days, base 60°F: 2,638

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	256	2	216
February	221	5	208
March	169	12	309
April	94	34	390
May	40	88	513
June	5	186	632
July	0	335	800
August	0	377	842
September	1	301	750
October	19	144	591
November	125	31	356
December	284	2	189

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 0.4 km from Escondido. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00042863 (Escondido #2). Public domain.