Geyserville climate

Geyserville Frost Dates and Growing Season

NOAA 1991-2020 normals for Healdsburg, 9.3 km from Geyserville, elevation 177 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Healdsburg. A median date has an even chance of a later freeze in spring, or an earlier one in fall.

The last spring freeze typically comes around February 15 and the first fall freeze around December 2, a growing season of about 292 days.

Median at 36°F
last March 29, first November 16
Median at 32°F
last February 15, first December 2
Median at 28°F
last January 7, first December 17

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.

Threshold10%20%30%40%50%60%70%80%90%
36°FApr 20Apr 13Apr 7Apr 2Mar 29Mar 23Mar 15Mar 8Feb 27
32°FMar 17Mar 6Feb 28Feb 23Feb 15Feb 8Jan 31Jan 21Jan 4
28°FFeb 2Jan 28Jan 21Jan 14Jan 7Jan 2Dec 29Dec 23Dec 14
24°FJan 28Jan 19Jan 13Jan 6Jan 1Dec 31Dec 24Dec 18Dec 10
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.

Threshold10%20%30%40%50%60%70%80%90%
36°FNov 1Nov 5Nov 9Nov 12Nov 16Nov 21Nov 24Nov 27Dec 2
32°FNov 14Nov 21Nov 26Nov 29Dec 2Dec 6Dec 10Dec 17Jan 1
28°FNov 28Dec 2Dec 7Dec 12Dec 17Dec 22Dec 30Jan 3Jan 12
24°FDec 4Dec 10Dec 15Dec 23Dec 30Jan 1Jan 7Jan 15Jan 25
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.

Threshold10%20%30%40%50%60%70%80%90%
36°F269256247240234228222214206
32°F334321310299292282274266254
28°F365365362354347341335330320
24°F365365365365365365365361348
20°F365365365365365365365365365
16°F365365365365365365365365365

How often it gets that cold

The share of years with at least one night at or below each temperature.

36°F or colder
100% of years
32°F or colder
99% of years
28°F or colder
70% of years
24°F or colder
22% of years
20°F or colder
3% 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
2,524
Cooling degree days, base 65°F
781
Growing degree days, base 40°F
7,386
Growing degree days, base 45°F
5,605
Growing degree days, base 50°F
3,988
Growing degree days, base 55°F
2,650
Growing degree days, base 60°F
1,584

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January512035
February385074
March3321152
April20311260
May8460442
June15158593
July2204667
August3189651
September15119554
October10938394
November3371138
December527031

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 9.3 km from Geyserville. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

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Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00043875 (Healdsburg). Public domain.