Seaside Frost Dates and Growing Season

NOAA 1991-2020 normals for Monterey WFO, 2 km from Seaside, elevation 122 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Monterey WFO. 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 47 percent of years at Monterey WFO, so there is no typical freeze season.

Median at 36°F: last February 1, first December 10
Median at 32°F: last January 3, first December 28

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 3	Feb 25	Feb 13	Feb 6	Feb 1	Jan 25	Jan 17	Jan 8	Dec 30
32°F	Jan 24	Jan 17	Jan 12	Jan 7	Jan 3	Dec 31	Dec 28	Dec 23	Dec 12
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 21	Nov 27	Dec 1	Dec 5	Dec 10	Dec 15	Dec 21	Dec 28	Jan 6
32°F	Dec 5	Dec 11	Dec 17	Dec 23	Dec 28	Jan 1	Jan 4	Jan 9	Jan 17
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	350	338	330	321	314	305	297	287	275
32°F	365	365	365	365	365	363	355	347	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: 97% of years
32°F or colder: 47% of years
28°F or colder: 6% 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: 3,330
Cooling degree days, base 65°F: 40
Growing degree days, base 40°F: 5,836
Growing degree days, base 45°F: 4,025
Growing degree days, base 50°F: 2,325
Growing degree days, base 55°F: 982
Growing degree days, base 60°F: 244

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	428	0	76
February	365	0	80
March	366	1	112
April	320	2	136
May	265	3	204
June	194	2	258
July	155	3	313
August	133	6	338
September	129	13	335
October	200	9	274
November	324	1	137
December	451	0	62

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 km from Seaside. 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 USC00045802 (Monterey WFO). Public domain.