Jackson climate

Jackson Frost Dates and Growing Season

NOAA 1991-2020 normals for Sutter Hill Cdf, 3.9 km from Jackson, elevation 1586 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Sutter Hill Cdf. 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 March 4 and the first fall freeze around December 11, a growing season of about 285 days.

Median at 36°F
last April 10, first November 25
Median at 32°F
last March 4, first December 11
Median at 28°F
last January 10, first December 27

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°FMay 4Apr 26Apr 20Apr 15Apr 10Apr 5Mar 31Mar 23Mar 9
32°FApr 8Mar 31Mar 21Mar 13Mar 4Feb 20Feb 4Jan 21Jan 6
28°FMar 2Feb 2Jan 24Jan 14Jan 10Jan 5Dec 31Dec 26Dec 14
24°FJan 13Jan 8Jan 3Dec 31Dec 28Dec 21Dec 18Dec 14Dec 10
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 1Nov 11Nov 17Nov 21Nov 25Nov 30Dec 3Dec 7Dec 12
32°FNov 19Nov 27Dec 2Dec 7Dec 11Dec 15Dec 20Dec 26Jan 4
28°FDec 2Dec 9Dec 14Dec 20Dec 27Jan 1Jan 6Jan 12Jan 26
24°FDec 9Dec 12Dec 15Dec 20Dec 25Dec 29Jan 1Jan 5Jan 10
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°F262249240235228220213205191
32°F343326310296285274262250234
28°F365365365365357349342333309
24°F365365365365365365365365353
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
99% of years
28°F or colder
62% of years
24°F or colder
17% 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
2,857
Cooling degree days, base 65°F
1,431
Growing degree days, base 40°F
7,724
Growing degree days, base 45°F
6,009
Growing degree days, base 50°F
4,486
Growing degree days, base 55°F
3,227
Growing degree days, base 60°F
2,228

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January558034
February427062
March4020115
April28612198
May13370404
June27221644
July2404868
August1370834
September16259693
October9990457
November3456149
December561030

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 3.9 km from Jackson. 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 USC00048713 (Sutter Hill Cdf). Public domain.