Graton climate

Graton Frost Dates and Growing Season

NOAA 1991-2020 normals for Graton, 0.8 km from Graton, elevation 200 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Graton. 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 20 and the first fall freeze around November 13, a growing season of about 240 days.

Median at 36°F
last April 23, first October 24
Median at 32°F
last March 20, first November 13
Median at 28°F
last February 1, first December 3

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 16May 6May 1Apr 27Apr 23Apr 19Apr 14Apr 8Mar 31
32°FApr 19Apr 10Apr 3Mar 28Mar 20Mar 13Mar 6Feb 27Feb 12
28°FMar 7Feb 27Feb 18Feb 10Feb 1Jan 27Jan 16Jan 3Dec 25
24°FJan 31Jan 23Jan 15Jan 7Jan 2Dec 29Dec 24Dec 14Dec 6
20°FJan 23Jan 11Jan 5Dec 31Dec 29Dec 23Dec 18Dec 11Dec 2
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°FSep 29Oct 8Oct 14Oct 19Oct 24Oct 28Nov 1Nov 5Nov 11
32°FOct 26Nov 1Nov 5Nov 9Nov 13Nov 18Nov 23Nov 29Dec 6
28°FNov 12Nov 19Nov 25Nov 30Dec 3Dec 7Dec 13Dec 26Jan 8
24°FNov 24Dec 1Dec 6Dec 12Dec 17Dec 25Jan 1Jan 6Jan 19
20°FDec 1Dec 4Dec 11Dec 15Dec 25Dec 29Jan 2Jan 9Jan 22
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°F215203196189182177169161149
32°F285267256247240232222213200
28°F347335325316307299290280266
24°F365365365364357350341334323
20°F365365365365365365365365360
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
100% of years
28°F or colder
95% of years
24°F or colder
55% of years
20°F or colder
11% 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
2,927
Cooling degree days, base 65°F
327
Growing degree days, base 40°F
6,531
Growing degree days, base 45°F
4,764
Growing degree days, base 50°F
3,190
Growing degree days, base 55°F
1,910
Growing degree days, base 60°F
943

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January538024
February402066
March3630127
April2673193
May16016321
June6054444
July2674513
August2285529
September4369476
October14325348
November3531124
December550026

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 0.8 km from Graton. 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 USC00043578 (Graton). Public domain.