Monterey Frost Dates and Growing Season

NOAA 1991-2020 normals for Monterey, 1.4 km from Monterey, elevation 260 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Monterey. 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 20 percent of years at Monterey, so there is no typical freeze season.

Median at 36°F: last January 19, first December 22
Median at 32°F: last January 1, first December 30

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 2	Feb 22	Feb 7	Jan 28	Jan 19	Jan 12	Jan 3	Dec 29	Dec 19
32°F	Jan 21	Jan 14	Jan 9	Jan 4	Jan 1	Dec 30	Dec 25	Dec 20	Dec 11
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 30	Dec 6	Dec 11	Dec 17	Dec 22	Dec 28	Jan 2	Jan 11	Jan 25
32°F	Dec 7	Dec 13	Dec 21	Dec 26	Dec 30	Jan 3	Jan 6	Jan 11	Jan 18
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	365	359	351	343	336	327	317	305	290
32°F	365	365	365	365	365	365	365	363	351
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: 84% of years
32°F or colder: 20% of years
28°F or colder: 2% 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: 3,083
Cooling degree days, base 65°F: 89
Growing degree days, base 40°F: 6,131
Growing degree days, base 45°F: 4,314
Growing degree days, base 50°F: 2,575
Growing degree days, base 55°F: 1,171
Growing degree days, base 60°F: 363

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	390	1	102
February	333	1	105
March	333	1	143
April	304	4	154
May	276	4	195
June	205	5	251
July	161	6	310
August	130	11	346
September	110	24	365
October	147	28	346
November	277	5	184
December	420	0	76

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 1.4 km from Monterey. 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 USC00045795 (Monterey). Public domain.