Marietta climate

Marietta Frost Dates and Growing Season

NOAA 1991-2020 normals for Marietta 5SW, 8.1 km from Marietta, elevation 802 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Marietta 5SW. 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 April 6 and the first fall freeze around November 2, a growing season of about 211 days.

Median at 36°F
last April 17, first October 23
Median at 32°F
last April 6, first November 2
Median at 28°F
last March 23, first November 9

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 1Apr 28Apr 24Apr 20Apr 17Apr 13Apr 10Apr 6Mar 31
32°FApr 24Apr 18Apr 13Apr 9Apr 6Apr 3Mar 30Mar 24Mar 16
28°FApr 11Apr 5Apr 1Mar 28Mar 23Mar 19Mar 15Mar 10Mar 3
24°FMar 31Mar 24Mar 19Mar 15Mar 11Mar 8Mar 4Feb 28Feb 21
20°FMar 18Mar 11Mar 7Mar 3Feb 27Feb 23Feb 15Feb 6Jan 29
16°FMar 6Feb 28Feb 22Feb 12Feb 6Jan 31Jan 27Jan 19Jan 6

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 8Oct 14Oct 18Oct 21Oct 23Oct 26Oct 29Nov 1Nov 5
32°FOct 18Oct 23Oct 27Oct 30Nov 2Nov 4Nov 7Nov 11Nov 16
28°FOct 24Oct 31Nov 3Nov 6Nov 9Nov 13Nov 16Nov 21Nov 27
24°FNov 2Nov 7Nov 12Nov 16Nov 21Nov 25Nov 29Dec 3Dec 9
20°FNov 12Nov 19Nov 25Nov 28Dec 2Dec 6Dec 12Dec 19Dec 27
16°FNov 25Dec 1Dec 6Dec 12Dec 20Dec 25Jan 1Jan 6Jan 16

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°F210203199194190186180175168
32°F234225220215211206200194186
28°F256247242236232226220214206
24°F282273267260254248242235226
20°F317306297289281275268259249
16°F351340331324316309302294280

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
95% 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
3,233
Cooling degree days, base 65°F
2,007
Growing degree days, base 40°F
8,200
Growing degree days, base 45°F
6,667
Growing degree days, base 50°F
5,277
Growing degree days, base 55°F
4,034
Growing degree days, base 60°F
2,943

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January764026
February574256
March39810168
April17446338
May40172597
June1377826
July0524989
August0513978
September15279714
October14775404
November4209142
December700139

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 8.1 km from Marietta. Low ground, valleys and open fields freeze earlier and later than a town center or a hillside.

More

Sources

NOAA NCEI U.S. Climate Normals, 1991-2020, annual and seasonal normals for station USC00345563 (Marietta 5SW). Public domain.