Isla Vista Frost Dates and Growing Season

NOAA 1991-2020 normals for Santa Barbara 11 W, 1.7 km from Isla Vista, elevation 18 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Santa Barbara 11 W. 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 46 percent of years at Santa Barbara 11 W, so there is no typical freeze season.

Median at 36°F: last February 3, first December 6
Median at 32°F: last December 31, first December 20

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 9	Feb 28	Feb 21	Feb 11	Feb 3	Jan 28	Jan 17	Jan 6	Dec 28
32°F	Jan 29	Jan 19	Jan 12	Jan 4	Dec 31	Dec 30	Dec 24	Dec 18	Dec 8
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 19	Nov 25	Nov 29	Dec 2	Dec 6	Dec 11	Dec 18	Dec 28	Jan 9
32°F	Dec 1	Dec 6	Dec 11	Dec 15	Dec 20	Dec 27	Jan 1	Jan 6	Jan 19
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	351	337	329	322	311	302	293	283	268
32°F	365	365	365	365	365	360	352	343	334
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: 95% of years
32°F or colder: 46% of years
28°F or colder: 10% 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: 2,498
Cooling degree days, base 65°F: 108
Growing degree days, base 40°F: 6,735
Growing degree days, base 45°F: 4,912
Growing degree days, base 50°F: 3,136
Growing degree days, base 55°F: 1,605
Growing degree days, base 60°F: 562

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	368	0	112
February	332	0	102
March	296	1	173
April	254	2	199
May	179	4	290
June	127	2	326
July	56	24	432
August	57	27	436
September	64	30	416
October	125	16	356
November	254	2	201
December	387	0	95

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 1.7 km from Isla Vista. 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 USW00053152 (Santa Barbara 11 W). Public domain.