Cambria Frost Dates and Growing Season

NOAA 1991-2020 normals for Hearst Castle, 15.5 km from Cambria, elevation 1526 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hearst Castle. 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 40 percent of years at Hearst Castle, so there is no typical freeze season.

Median at 36°F: last March 13, first December 25
Median at 32°F: last February 13, first February 1

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 24	Apr 14	Apr 6	Mar 27	Mar 13	Mar 1	Feb 22	Feb 11	Jan 21
32°F	Mar 31	Mar 11	Feb 27	Feb 21	Feb 13	Feb 3	Jan 19	Jan 8	Dec 29
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 26	Dec 5	Dec 11	Dec 18	Dec 25	Jan 1	Jan 8	Jan 28	Feb 20
32°F	Dec 16	Jan 2	Jan 8	Jan 20	Feb 1	Feb 11	Feb 21	Feb 27	Mar 20
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	349	327	308	296	283	272	262	254	242
32°F	365	365	365	365	365	365	353	322	306
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: 40% 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: 2,618
Cooling degree days, base 65°F: 780
Growing degree days, base 40°F: 7,288
Growing degree days, base 45°F: 5,493
Growing degree days, base 50°F: 3,841
Growing degree days, base 55°F: 2,465
Growing degree days, base 60°F: 1,449

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	373	5	144
February	356	4	116
March	330	8	175
April	285	19	201
May	200	59	328
June	122	89	417
July	93	126	498
August	64	151	552
September	52	175	573
October	109	114	470
November	239	28	250
December	395	3	117

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 15.5 km from Cambria. 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 USC00043882 (Hearst Castle). Public domain.