Griffin climate

Griffin Frost Dates and Growing Season

NOAA 1991-2020 normals for Experiment, 2.6 km from Griffin, elevation 934 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Experiment. 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 239 days.

Median at 36°F
last April 4, first November 1
Median at 32°F
last March 20, first November 13
Median at 28°F
last March 2, first November 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°FApr 22Apr 16Apr 12Apr 8Apr 4Apr 1Mar 28Mar 20Mar 13
32°FApr 10Apr 3Mar 29Mar 25Mar 20Mar 15Mar 9Mar 3Feb 25
28°FMar 25Mar 17Mar 12Mar 6Mar 2Feb 27Feb 23Feb 18Feb 8
24°FMar 12Mar 3Feb 27Feb 23Feb 18Feb 13Feb 6Jan 31Jan 20
20°FFeb 28Feb 21Feb 15Feb 9Feb 3Jan 31Jan 24Jan 17Jan 4
16°FFeb 21Feb 10Feb 5Feb 1Jan 28Jan 22Jan 16Jan 9Jan 1

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 21Oct 25Oct 27Oct 30Nov 1Nov 4Nov 7Nov 11Nov 18
32°FOct 31Nov 3Nov 6Nov 10Nov 13Nov 16Nov 21Nov 27Dec 3
28°FNov 9Nov 14Nov 19Nov 25Nov 29Dec 2Dec 7Dec 14Dec 24
24°FNov 23Nov 30Dec 5Dec 10Dec 16Dec 23Dec 30Jan 4Jan 13
20°FDec 8Dec 15Dec 24Dec 31Jan 4Jan 8Jan 16Jan 25Feb 4
16°FDec 20Dec 30Jan 4Jan 9Jan 15Jan 20Jan 26Feb 2Feb 10

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°F237228222216211207202197189
32°F268257250245239234228221211
28°F303290282274268263258250241
24°F332323315310304297290282270
20°F365353343335330324317310300
16°F365365365365356345337331319

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
99% of years
20°F or colder
87% of years
16°F or colder
57% 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
2,589
Cooling degree days, base 65°F
1,805
Growing degree days, base 40°F
8,441
Growing degree days, base 45°F
6,785
Growing degree days, base 50°F
5,284
Growing degree days, base 55°F
3,952
Growing degree days, base 60°F
2,789

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January622045
February484166
March30815222
April13750369
May24184625
June1350799
July0446911
August0411876
September7268711
October11168426
November34311171
December553163

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 2.6 km from Griffin. 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 USC00093271 (Experiment). Public domain.