Callender Frost Dates and Growing Season

NOAA 1991-2020 normals for Pismo Beach, 14.3 km from Callender, elevation 39 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Pismo Beach. 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 1 and the first fall freeze around January 4, a growing season of about 362 days.

Median at 36°F: last March 1, first December 14
Median at 32°F: last February 1, first January 4

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	Apr 12	Mar 29	Mar 18	Mar 9	Mar 1	Feb 23	Feb 14	Jan 29	Jan 7
32°F	Mar 13	Feb 28	Feb 21	Feb 12	Feb 1	Jan 17	Jan 4	Dec 31	Dec 18
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 22	Nov 29	Dec 2	Dec 8	Dec 14	Dec 21	Dec 27	Jan 4	Jan 21
32°F	Dec 8	Dec 18	Dec 26	Dec 31	Jan 4	Jan 16	Jan 31	Feb 12	Feb 27
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	344	325	312	299	288	276	266	253	239
32°F	365	365	365	365	362	350	334	316	299
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: 98% of years
32°F or colder: 54% of years
28°F or colder: 7% 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: 2,262
Cooling degree days, base 65°F: 119
Growing degree days, base 40°F: 6,983
Growing degree days, base 45°F: 5,159
Growing degree days, base 50°F: 3,364
Growing degree days, base 55°F: 1,763
Growing degree days, base 60°F: 617

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	327	1	147
February	293	1	136
March	258	5	218
April	194	12	270
May	144	17	338
June	132	11	328
July	99	9	375
August	71	12	406
September	84	17	383
October	106	29	389
November	224	5	233
December	331	1	141

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 14.3 km from Callender. 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 USC00046943 (Pismo Beach). Public domain.