Collegedale climate

Collegedale Frost Dates and Growing Season

NOAA 1991-2020 normals for Chattanooga Lovell AP, 14 km from Collegedale, elevation 671 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Chattanooga Lovell AP. 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 24 and the first fall freeze around November 9, a growing season of about 230 days.

Median at 36°F
last April 4, first October 31
Median at 32°F
last March 24, first November 9
Median at 28°F
last March 11, first November 22

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 20Apr 14Apr 10Apr 7Apr 4Apr 1Mar 29Mar 25Mar 19
32°FApr 8Apr 3Mar 31Mar 28Mar 24Mar 20Mar 16Mar 12Mar 6
28°FMar 30Mar 23Mar 18Mar 15Mar 11Mar 7Mar 2Feb 25Feb 18
24°FMar 18Mar 11Mar 5Feb 28Feb 23Feb 18Feb 12Feb 3Jan 26
20°FMar 4Feb 25Feb 16Feb 9Feb 4Jan 31Jan 26Jan 19Jan 9
16°FFeb 23Feb 7Feb 1Jan 28Jan 24Jan 18Jan 12Jan 8Jan 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 19Oct 23Oct 26Oct 28Oct 31Nov 1Nov 4Nov 7Nov 11
32°FOct 27Nov 1Nov 3Nov 6Nov 9Nov 11Nov 14Nov 18Nov 26
28°FNov 6Nov 10Nov 14Nov 18Nov 22Nov 26Dec 1Dec 5Dec 13
24°FNov 16Nov 23Nov 30Dec 4Dec 8Dec 14Dec 21Dec 28Jan 5
20°FDec 4Dec 12Dec 21Dec 27Dec 31Jan 3Jan 8Jan 14Jan 25
16°FDec 21Dec 29Jan 2Jan 5Jan 9Jan 13Jan 17Jan 24Jan 31

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°F228221216212208204200196189
32°F254245240235230226222216210
28°F285274267262257251247241233
24°F322311304296289282275267258
20°F357343336330324317309303288
16°F365365363353346340334326312

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
94% of years
16°F or colder
73% 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
3,029
Cooling degree days, base 65°F
1,921
Growing degree days, base 40°F
8,215
Growing degree days, base 45°F
6,638
Growing degree days, base 50°F
5,216
Growing degree days, base 55°F
3,958
Growing degree days, base 60°F
2,864

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January723031
February544148
March37710167
April14750360
May30185620
June1374823
July0488953
August0465930
September7276718
October13565402
November4215119
December644144

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 14 km from Collegedale. 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 USW00013882 (Chattanooga Lovell AP). Public domain.