Fairview Frost Dates and Growing Season

NOAA 1991-2020 normals for Hayward Air Terminal, 6.7 km from Fairview, elevation 43 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hayward Air Terminal. 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 45 percent of years at Hayward Air Terminal, so there is no typical freeze season.

Median at 36°F: last January 29, first December 12
Median at 32°F: last January 2, first December 25

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	Feb 28	Feb 21	Feb 11	Feb 3	Jan 29	Jan 22	Jan 14	Jan 7	Dec 30
32°F	Jan 27	Jan 18	Jan 12	Jan 7	Jan 2	Dec 31	Dec 27	Dec 22	Dec 13
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 24	Dec 1	Dec 4	Dec 8	Dec 12	Dec 16	Dec 22	Dec 31	Jan 11
32°F	Dec 6	Dec 11	Dec 17	Dec 21	Dec 25	Dec 29	Jan 2	Jan 9	Jan 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	358	347	336	330	322	310	302	291	277
32°F	365	365	365	365	365	361	355	348	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: 93% of years
32°F or colder: 45% of years
28°F or colder: 5% 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: 2,315
Cooling degree days, base 65°F: 367
Growing degree days, base 40°F: 7,177
Growing degree days, base 45°F: 5,362
Growing degree days, base 50°F: 3,627
Growing degree days, base 55°F: 2,142
Growing degree days, base 60°F: 1,040

Growing degree days by month, base 50°F

Heating and cooling by month

Month	Heating DD	Cooling DD	Growing DD 50
January	428	0	73
February	322	0	113
March	285	2	188
April	214	9	245
May	149	21	336
June	64	51	437
July	29	62	498
August	15	86	536
September	25	94	519
October	88	41	419
November	268	2	191
December	429	0	74

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 6.7 km from Fairview. 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 USW00093228 (Hayward Air Terminal). Public domain.