Montgomery County climate

Montgomery County Frost Dates and Growing Season

NOAA 1991-2020 normals for Clarksville Wwtp, 7 km from Montgomery County, elevation 402 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Clarksville Wwtp. 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 3 and the first fall freeze around November 1, a growing season of about 212 days.

Median at 36°F
last April 16, first October 23
Median at 32°F
last April 3, first November 1
Median at 28°F
last March 22, first November 11

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

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°F208201196193189185181177171
32°F233225221216212207203199192
28°F260250244239235230226220213
24°F285276271264259254249241233
20°F313302295288282276270263254
16°F341330323317309304297288278

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
99% 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
3,757
Cooling degree days, base 65°F
1,662
Growing degree days, base 40°F
7,484
Growing degree days, base 45°F
6,028
Growing degree days, base 50°F
4,716
Growing degree days, base 55°F
3,552
Growing degree days, base 60°F
2,533

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January859020
February670134
March4847121
April21042307
May53149561
June2326774
July0448913
August0419883
September21222651
October19944327
November502494
December757032

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 7 km from Montgomery County. 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 USC00401790 (Clarksville Wwtp). Public domain.