Ahwahnee climate

Ahwahnee Frost Dates and Growing Season

NOAA 1991-2020 normals for So Entrance Yosemite Np, 18.2 km from Ahwahnee, elevation 5047 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for So Entrance Yosemite Np. 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 24 and the first fall freeze around October 10, a growing season of about 137 days.

Median at 36°F
last June 8, first September 26
Median at 32°F
last May 24, first October 10
Median at 28°F
last May 3, first October 29

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 26Jun 19Jun 15Jun 11Jun 8Jun 5Jun 3May 31May 23
32°FJun 11Jun 5Jun 1May 30May 24May 19May 14May 10May 3
28°FMay 29May 19May 13May 8May 3Apr 30Apr 26Apr 21Apr 14
24°FMay 7Apr 29Apr 21Apr 17Apr 13Apr 9Apr 6Apr 2Mar 22
20°FApr 17Apr 9Apr 4Mar 30Mar 22Mar 15Mar 8Feb 28Feb 13
16°FMar 26Mar 12Mar 2Feb 23Feb 13Feb 5Jan 24Jan 9Dec 31

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 7Sep 14Sep 20Sep 23Sep 26Sep 30Oct 3Oct 7Oct 13
32°FSep 24Sep 30Oct 2Oct 6Oct 10Oct 13Oct 18Oct 24Nov 1
28°FOct 3Oct 12Oct 19Oct 24Oct 29Nov 1Nov 4Nov 9Nov 15
24°FOct 27Nov 2Nov 8Nov 13Nov 17Nov 21Nov 25Nov 30Dec 6
20°FNov 14Nov 20Nov 24Nov 28Dec 1Dec 5Dec 10Dec 16Dec 27
16°FNov 24Dec 1Dec 6Dec 11Dec 17Dec 23Jan 1Jan 10Jan 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°F129121116111107102979183
32°F163156149143137132126119112
28°F204194187180173167161153140
24°F246235228221215209201194182
20°F300282272263256248241232221
16°F360342332322311300289276262

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
100% of years
16°F or colder
93% 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
6,225
Cooling degree days, base 65°F
152
Growing degree days, base 40°F
3,775
Growing degree days, base 45°F
2,645
Growing degree days, base 50°F
1,747
Growing degree days, base 55°F
1,033
Growing degree days, base 60°F
493

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January90400
February80600
March80803
April668017
May4582106
June21015271
July5567477
August6452453
September17516302
October4471103
November705014
December92700

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 18.2 km from Ahwahnee. 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 USC00048380 (So Entrance Yosemite Np). Public domain.