San Ardo climate

San Ardo Frost Dates and Growing Season

NOAA 1991-2020 normals for Priest Valley, 26.5 km from San Ardo, elevation 2300 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Priest Valley. 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 May 8 and the first fall freeze around October 22, a growing season of about 165 days.

Median at 36°F
last May 31, first October 3
Median at 32°F
last May 8, first October 22
Median at 28°F
last April 15, first November 5

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°FJun 16Jun 9Jun 6Jun 3May 31May 27May 24May 19May 12
32°FMay 29May 23May 17May 13May 8May 3Apr 30Apr 26Apr 20
28°FMay 8May 1Apr 25Apr 20Apr 15Apr 11Apr 7Apr 1Mar 23
24°FApr 12Apr 5Mar 28Mar 18Mar 10Feb 28Feb 20Feb 8Jan 26
20°FMar 1Feb 21Feb 9Feb 1Jan 27Jan 17Jan 6Dec 29Dec 15
16°FFeb 7Jan 31Jan 22Jan 15Jan 5Dec 31Dec 23Dec 14Dec 3

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°FSep 8Sep 19Sep 26Oct 1Oct 3Oct 7Oct 11Oct 17Oct 23
32°FOct 1Oct 7Oct 13Oct 18Oct 22Oct 26Oct 31Nov 3Nov 8
28°FOct 19Oct 24Oct 30Nov 2Nov 5Nov 8Nov 12Nov 16Nov 25
24°FNov 2Nov 7Nov 11Nov 16Nov 21Nov 25Nov 30Dec 5Dec 17
20°FNov 16Nov 22Nov 27Dec 1Dec 4Dec 13Dec 23Jan 2Jan 16
16°FNov 26Dec 1Dec 5Dec 11Dec 16Dec 29Jan 3Jan 13Feb 1

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°F15114313513012411911410593
32°F192183177171165158153146137
28°F236222214208203197190183173
24°F309292280268257247238228217
20°F365345334327318310303292276
16°F365365365365361349340333321

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
100% of years
28°F or colder
100% of years
24°F or colder
100% of years
20°F or colder
89% of years
16°F or colder
47% 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
3,603
Cooling degree days, base 65°F
845
Growing degree days, base 40°F
6,418
Growing degree days, base 45°F
4,782
Growing degree days, base 50°F
3,412
Growing degree days, base 55°F
2,334
Growing degree days, base 60°F
1,500

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January631010
February514022
March485058
April3641119
May19026306
June48117519
July4265727
August3269732
September33146563
October20921283
November473063
December651010

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 26.5 km from San Ardo. 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 USC00047150 (Priest Valley). Public domain.