El Centro Frost Dates and Growing Season

NOAA 1991-2020 normals for El Centro 2 Ssw, 2.8 km from El Centro, elevation -30 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for El Centro 2 Ssw. 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 3 and the first fall freeze around December 27, a growing season of about 363 days.

Median at 36°F: last January 22, first December 17
Median at 32°F: last January 3, first December 27
Median at 28°F: last January 1, first December 31

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	Feb 22	Feb 12	Feb 4	Jan 29	Jan 22	Jan 15	Jan 9	Jan 3	Dec 27
32°F	Feb 4	Jan 25	Jan 15	Jan 8	Jan 3	Dec 31	Dec 28	Dec 23	Dec 15
28°F	Feb 4	Jan 20	Jan 10	Jan 6	Jan 1	Dec 29	Dec 26	Dec 23	Dec 15
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 30	Dec 6	Dec 10	Dec 14	Dec 17	Dec 20	Dec 24	Dec 30	Jan 9
32°F	Dec 9	Dec 16	Dec 21	Dec 24	Dec 27	Dec 31	Jan 3	Jan 12	Jan 26
28°F	Dec 15	Dec 23	Dec 26	Dec 29	Dec 31	Jan 3	Jan 10	Jan 20	Feb 4
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	341	334	327	319	313	304	294
32°F	365	365	365	365	363	357	351	342	332
28°F	365	365	365	365	365	365	365	365	361
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: 54% of years
28°F or colder: 14% 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: 834
Cooling degree days, base 65°F: 4,247
Growing degree days, base 40°F: 12,538
Growing degree days, base 45°F: 10,714
Growing degree days, base 50°F: 8,902
Growing degree days, base 55°F: 7,162
Growing degree days, base 60°F: 5,592

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	244	2	228
February	148	17	292
March	64	93	494
April	15	211	647
May	2	422	885
June	0	654	1,104
July	0	851	1,316
August	0	868	1,333
September	0	678	1,128
October	4	366	828
November	84	82	449
December	275	2	199

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 2.8 km from El Centro. 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 USC00042713 (El Centro 2 Ssw). Public domain.