Yolo County climate

Yolo County Frost Dates and Growing Season

NOAA 1991-2020 normals for Woodland 1 Wnw, 9.4 km from Yolo County, elevation 67 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Woodland 1 Wnw. 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 7 and the first fall freeze around December 5, a growing season of about 301 days.

Median at 36°F
last March 15, first November 20
Median at 32°F
last February 7, first December 5
Median at 28°F
last January 10, first December 18

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 12Apr 3Mar 28Mar 22Mar 15Mar 9Mar 5Feb 27Feb 15
32°FMar 11Mar 2Feb 24Feb 16Feb 7Feb 2Jan 29Jan 20Jan 9
28°FFeb 2Jan 27Jan 21Jan 15Jan 10Jan 4Dec 31Dec 25Dec 14
24°FJan 22Jan 15Jan 6Jan 2Dec 31Dec 29Dec 25Dec 20Dec 11
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 4Nov 10Nov 13Nov 17Nov 20Nov 23Nov 26Nov 29Dec 5
32°FNov 19Nov 25Nov 29Dec 1Dec 5Dec 9Dec 12Dec 19Jan 1
28°FDec 1Dec 5Dec 9Dec 13Dec 18Dec 23Dec 31Jan 5Jan 16
24°FDec 7Dec 13Dec 18Dec 24Dec 27Dec 30Jan 2Jan 7Jan 18
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°F280268260253246240232225215
32°F336325316308301294285273260
28°F365365359353347341336332320
24°F365365365365365365365361349
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
98% of years
28°F or colder
71% of years
24°F or colder
24% of years
20°F or colder
1% 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
2,432
Cooling degree days, base 65°F
1,416
Growing degree days, base 40°F
8,119
Growing degree days, base 45°F
6,356
Growing degree days, base 50°F
4,768
Growing degree days, base 55°F
3,427
Growing degree days, base 60°F
2,317

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January561020
February386072
March2913191
April16225316
May54117529
June7253696
July0358823
August0335800
September5247691
October7576467
November3311143
December560022

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 9.4 km from Yolo County. 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 USC00049781 (Woodland 1 Wnw). Public domain.