Gratton climate

Gratton Frost Dates and Growing Season

NOAA 1991-2020 normals for Burkes Garden, 8.5 km from Gratton, elevation 3068 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Burkes Garden. 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 9 and the first fall freeze around October 6, a growing season of about 150 days.

Median at 36°F
last May 20, first September 27
Median at 32°F
last May 9, first October 6
Median at 28°F
last April 28, first October 15

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 4May 31May 27May 24May 20May 17May 13May 9May 2
32°FMay 26May 20May 16May 12May 9May 5May 1Apr 28Apr 23
28°FMay 16May 10May 5May 1Apr 28Apr 23Apr 20Apr 16Apr 9
24°FMay 5Apr 27Apr 21Apr 16Apr 13Apr 8Apr 5Apr 1Mar 28
20°FApr 17Apr 10Apr 5Apr 2Mar 31Mar 27Mar 22Mar 18Mar 13
16°FApr 5Mar 31Mar 26Mar 21Mar 17Mar 13Mar 8Mar 2Feb 25

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 10Sep 16Sep 20Sep 24Sep 27Sep 29Oct 2Oct 5Oct 10
32°FSep 20Sep 26Oct 1Oct 3Oct 6Oct 8Oct 12Oct 15Oct 20
28°FOct 2Oct 6Oct 10Oct 13Oct 15Oct 19Oct 22Oct 25Oct 30
24°FOct 11Oct 15Oct 20Oct 22Oct 26Oct 29Nov 1Nov 3Nov 8
20°FOct 19Oct 24Oct 28Nov 1Nov 3Nov 6Nov 9Nov 13Nov 22
16°FOct 29Nov 3Nov 7Nov 11Nov 14Nov 18Nov 23Nov 28Dec 3

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°F149142136132127122119113105
32°F171165159154150146141135128
28°F193187181177172168162157149
24°F217210204200196191187181172
20°F242234228222217213209204197
16°F272262254247243237231226218

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
100% 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
5,967
Cooling degree days, base 65°F
301
Growing degree days, base 40°F
4,601
Growing degree days, base 45°F
3,399
Growing degree days, base 50°F
2,370
Growing degree days, base 55°F
1,501
Growing degree days, base 60°F
801

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,08204
February90605
March784026
April477199
May25212251
June6959440
July22116559
August3684513
September15227333
October4613110
November747023
December98007

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 8.5 km from Gratton. 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 USC00441209 (Burkes Garden). Public domain.