Walden climate

Walden Frost Dates and Growing Season

NOAA 1991-2020 normals for Soddy Daisy-Mowbray Mtn, 13.9 km from Walden, elevation 1700 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Soddy Daisy-Mowbray Mtn. 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 7 and the first fall freeze around October 29, a growing season of about 203 days.

Median at 36°F
last April 20, first October 20
Median at 32°F
last April 7, first October 29
Median at 28°F
last March 27, first November 8

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 8May 2Apr 29Apr 24Apr 20Apr 17Apr 13Apr 8Apr 2
32°FApr 28Apr 20Apr 15Apr 11Apr 7Apr 3Mar 31Mar 27Mar 20
28°FApr 13Apr 6Apr 2Mar 31Mar 27Mar 23Mar 19Mar 14Mar 6
24°FApr 2Mar 28Mar 24Mar 19Mar 15Mar 11Mar 5Feb 28Feb 21
20°FMar 24Mar 17Mar 12Mar 6Mar 1Feb 25Feb 19Feb 12Feb 3
16°FMar 15Mar 6Feb 28Feb 22Feb 15Feb 8Feb 3Jan 28Jan 17

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 5Oct 10Oct 14Oct 17Oct 20Oct 22Oct 25Oct 28Nov 2
32°FOct 13Oct 19Oct 22Oct 26Oct 29Nov 1Nov 3Nov 7Nov 12
28°FOct 23Oct 30Nov 1Nov 5Nov 8Nov 12Nov 16Nov 20Nov 28
24°FNov 5Nov 10Nov 15Nov 20Nov 25Nov 29Dec 2Dec 7Dec 16
20°FNov 18Nov 27Dec 1Dec 5Dec 11Dec 18Dec 25Jan 1Jan 8
16°FDec 3Dec 11Dec 21Dec 27Jan 1Jan 4Jan 8Jan 15Jan 26

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°F204196191185181176171164157
32°F229221214209203199193187178
28°F255246239233228223217212203
24°F288275268261256250244236227
20°F319306300293286279273264253
16°F344334326318311306300291281

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
97% 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
3,793
Cooling degree days, base 65°F
1,275
Growing degree days, base 40°F
7,022
Growing degree days, base 45°F
5,555
Growing degree days, base 50°F
4,237
Growing degree days, base 55°F
3,092
Growing degree days, base 60°F
2,105

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January835017
February662025
March4964113
April22331285
May72109504
June5246691
July0363828
August1330793
September33162580
October22929291
November497177
December740134

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 13.9 km from Walden. 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 USC00408445 (Soddy Daisy-Mowbray Mtn). Public domain.