Tuolumne County climate

Tuolumne County Frost Dates and Growing Season

NOAA 1991-2020 normals for Cherry Valley Dam, 6.8 km from Tuolumne County, elevation 4765 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Cherry Valley Dam. 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 2 and the first fall freeze around November 4, a growing season of about 183 days.

Median at 36°F
last May 21, first October 19
Median at 32°F
last May 2, first November 4
Median at 28°F
last April 16, first November 20

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 9Jun 3May 31May 26May 21May 16May 12May 7May 1
32°FMay 29May 20May 13May 8May 2Apr 28Apr 24Apr 19Apr 14
28°FMay 10Apr 30Apr 24Apr 19Apr 16Apr 11Apr 7Apr 2Mar 23
24°FApr 21Apr 14Apr 8Apr 3Mar 27Mar 19Mar 10Mar 1Feb 15
20°FApr 1Mar 15Mar 6Feb 28Feb 21Feb 10Feb 3Jan 20Jan 3
16°FFeb 27Feb 19Feb 9Feb 2Jan 24Jan 17Jan 6Jan 1Dec 21

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°FOct 1Oct 6Oct 11Oct 16Oct 19Oct 24Oct 29Nov 2Nov 7
32°FOct 15Oct 22Oct 28Nov 1Nov 4Nov 8Nov 11Nov 15Nov 22
28°FNov 1Nov 8Nov 12Nov 16Nov 20Nov 24Nov 28Dec 2Dec 7
24°FNov 15Nov 23Nov 28Dec 1Dec 5Dec 8Dec 12Dec 18Dec 24
20°FNov 29Dec 6Dec 12Dec 18Dec 23Dec 28Jan 2Jan 15Jan 31
16°FDec 10Dec 20Dec 27Jan 1Jan 6Jan 17Jan 24Feb 4Feb 17

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°F180169164158153147140134124
32°F210201194188183177170162151
28°F248237229222217211204196186
24°F293279268259251244237230218
20°F348333321309301291280270257
16°F365365365362352340328314301

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
96% of years
16°F or colder
62% 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
4,564
Cooling degree days, base 65°F
812
Growing degree days, base 40°F
5,722
Growing degree days, base 45°F
4,335
Growing degree days, base 50°F
3,174
Growing degree days, base 55°F
2,221
Growing degree days, base 60°F
1,436

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January76406
February673011
March640034
April479191
May27524255
June80109484
July5273733
August4257718
September56130526
October25720257
November552056
December77804

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 6.8 km from Tuolumne 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 USC00041697 (Cherry Valley Dam). Public domain.