Rydal climate

Rydal Frost Dates and Growing Season

NOAA 1991-2020 normals for Allatoona Dam 2, 19 km from Rydal, elevation 975 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Allatoona Dam 2. 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 2 and the first fall freeze around November 4, a growing season of about 215 days.

Median at 36°F
last April 13, first October 26
Median at 32°F
last April 2, first November 4
Median at 28°F
last March 20, first November 14

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 30Apr 24Apr 21Apr 17Apr 13Apr 10Apr 7Apr 3Mar 30
32°FApr 19Apr 12Apr 8Apr 5Apr 2Mar 30Mar 26Mar 21Mar 14
28°FApr 6Apr 1Mar 28Mar 24Mar 20Mar 16Mar 12Mar 5Feb 28
24°FMar 26Mar 20Mar 15Mar 10Mar 6Mar 2Feb 26Feb 20Feb 12
20°FMar 16Mar 8Mar 2Feb 27Feb 21Feb 14Feb 7Jan 31Jan 21
16°FMar 3Feb 24Feb 14Feb 7Feb 2Jan 29Jan 23Jan 16Jan 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 13Oct 17Oct 20Oct 23Oct 26Oct 28Oct 31Nov 3Nov 8
32°FOct 21Oct 26Oct 30Nov 1Nov 4Nov 6Nov 10Nov 14Nov 21
28°FOct 30Nov 4Nov 7Nov 10Nov 14Nov 17Nov 22Nov 27Dec 4
24°FNov 7Nov 14Nov 19Nov 24Nov 29Dec 2Dec 7Dec 14Dec 26
20°FNov 22Dec 1Dec 5Dec 12Dec 21Dec 27Jan 1Jan 6Jan 16
16°FDec 7Dec 17Dec 26Dec 31Jan 3Jan 8Jan 14Jan 21Feb 1

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°F215208202198194190186181174
32°F239231225219215211206201193
28°F267257250244239234228222214
24°F299288280275268263255248238
20°F334320311304298291284277265
16°F365353342335329320312304295

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
99% of years
16°F or colder
89% 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
3,408
Cooling degree days, base 65°F
1,479
Growing degree days, base 40°F
7,466
Growing degree days, base 45°F
5,947
Growing degree days, base 50°F
4,588
Growing degree days, base 55°F
3,387
Growing degree days, base 60°F
2,352

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January777024
February604032
March4395130
April20231297
May54129540
June4286732
July0392857
August0378843
September16214648
October17142348
November4592101
December683137

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 19 km from Rydal. 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 USC00090181 (Allatoona Dam 2). Public domain.