Yosemite Valley climate

Yosemite Valley Frost Dates and Growing Season

NOAA 1991-2020 normals for Yosemite Park Hq, 1.5 km from Yosemite Valley, elevation 4018 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Yosemite Park Hq. 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 April 21 and the first fall freeze around October 27, a growing season of about 186 days.

Median at 36°F
last May 10, first October 16
Median at 32°F
last April 21, first October 27
Median at 28°F
last April 2, first November 9

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 3May 28May 21May 14May 10May 5May 2Apr 28Apr 22
32°FMay 13May 5Apr 30Apr 26Apr 21Apr 17Apr 13Apr 9Apr 3
28°FApr 22Apr 15Apr 12Apr 7Apr 2Mar 28Mar 21Mar 14Mar 5
24°FApr 4Mar 28Mar 19Mar 11Mar 5Feb 28Feb 22Feb 12Feb 1
20°FMar 9Feb 27Feb 20Feb 11Feb 4Jan 25Jan 15Jan 6Dec 26
16°FFeb 14Feb 5Jan 24Jan 14Jan 8Jan 2Dec 30Dec 23Dec 12

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 8Oct 11Oct 14Oct 16Oct 19Oct 23Oct 27Nov 1
32°FOct 12Oct 17Oct 20Oct 24Oct 27Oct 31Nov 3Nov 7Nov 10
28°FOct 20Oct 26Oct 31Nov 4Nov 9Nov 12Nov 16Nov 21Nov 28
24°FOct 31Nov 8Nov 17Nov 23Nov 27Dec 1Dec 5Dec 9Dec 17
20°FNov 19Nov 29Dec 5Dec 9Dec 15Dec 21Dec 27Jan 4Jan 20
16°FDec 2Dec 10Dec 17Dec 23Dec 28Jan 1Jan 6Jan 15Jan 30

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°F182175170163157151146138127
32°F212204197192186181175168160
28°F252241232226220213208200189
24°F305291278271264256249240228
20°F358346335325314306296286269
16°F365365365365359353344334318

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
95% of years
16°F or colder
58% 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
4,741
Cooling degree days, base 65°F
754
Growing degree days, base 40°F
5,507
Growing degree days, base 45°F
4,176
Growing degree days, base 50°F
3,061
Growing degree days, base 55°F
2,126
Growing degree days, base 60°F
1,362

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January83700
February68006
March617030
April440098
May24715260
June7496476
July4261722
August4248710
September53118517
October29115218
November622024
December87200

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 1.5 km from Yosemite Valley. 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 USC00049855 (Yosemite Park Hq). Public domain.