Bodega Bay Frost Dates and Growing Season

NOAA 1991-2020 normals for Bodega 6 Wsw, 2.7 km from Bodega Bay, elevation 63 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Bodega 6 Wsw. 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 18 percent of years at Bodega 6 Wsw, so there is no typical freeze season.

Median at 36°F: last February 13, first December 17
Median at 32°F: last January 1, first December 31

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 4	Mar 14	Mar 2	Feb 23	Feb 13	Jan 30	Jan 13	Jan 1	Dec 21
32°F	Feb 24	Feb 18	Feb 3	Jan 9	Jan 1	Dec 29	Dec 23	Dec 15	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 21	Nov 30	Dec 5	Dec 11	Dec 17	Dec 26	Jan 3	Jan 19	Feb 14
32°F	Dec 6	Dec 11	Dec 20	Dec 25	Dec 31	Jan 6	Jan 25	Feb 15	Feb 22
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	352	338	324	310	301	288	274	258
32°F	365	365	365	365	365	365	365	365	338
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: 85% of years
32°F or colder: 18% of years
28°F or colder: 0% 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: 4,188
Cooling degree days, base 65°F: 4
Growing degree days, base 40°F: 4,941
Growing degree days, base 45°F: 3,131
Growing degree days, base 50°F: 1,463
Growing degree days, base 55°F: 373
Growing degree days, base 60°F: 46

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	453	0	49
February	406	0	51
March	425	0	61
April	407	0	56
May	370	0	97
June	300	0	150
July	264	0	202
August	236	1	229
September	204	2	249
October	289	0	179
November	366	0	96
December	470	0	46

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 2.7 km from Bodega Bay. 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 USW00093245 (Bodega 6 Wsw). Public domain.