Putnam County climate

Putnam County Frost Dates and Growing Season

NOAA 1991-2020 normals for Unionville, 1.2 km from Putnam County, elevation 1060 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Unionville. 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 17 and the first fall freeze around October 22, a growing season of about 186 days.

Median at 36°F
last April 28, first October 11
Median at 32°F
last April 17, first October 22
Median at 28°F
last April 8, first October 31

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 9May 5May 2Apr 30Apr 28Apr 25Apr 21Apr 18Apr 14
32°FApr 30Apr 26Apr 23Apr 20Apr 17Apr 15Apr 12Apr 9Apr 4
28°FApr 22Apr 18Apr 14Apr 11Apr 8Apr 6Apr 3Mar 31Mar 25
24°FApr 14Apr 9Apr 6Apr 3Mar 31Mar 28Mar 24Mar 20Mar 13
20°FApr 6Apr 1Mar 28Mar 25Mar 21Mar 18Mar 14Mar 9Mar 4
16°FMar 29Mar 23Mar 19Mar 15Mar 12Mar 9Mar 5Mar 2Feb 26

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°FSep 27Oct 1Oct 5Oct 8Oct 11Oct 14Oct 17Oct 20Oct 24
32°FOct 7Oct 12Oct 16Oct 19Oct 22Oct 24Oct 26Oct 29Nov 1
28°FOct 19Oct 22Oct 25Oct 28Oct 31Nov 1Nov 3Nov 6Nov 12
24°FOct 26Oct 31Nov 1Nov 3Nov 6Nov 8Nov 12Nov 16Nov 21
20°FNov 2Nov 5Nov 9Nov 12Nov 16Nov 19Nov 23Nov 28Dec 2
16°FNov 7Nov 13Nov 17Nov 20Nov 24Nov 29Dec 1Dec 5Dec 11

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°F183177172169165161157153146
32°F203197193189186182178174168
28°F223216212208205201197192185
24°F242236230226222217213209203
20°F264255248243239235231226218
16°F279271266262257252247241234

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
100% 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
6,103
Cooling degree days, base 65°F
986
Growing degree days, base 40°F
5,577
Growing degree days, base 45°F
4,402
Growing degree days, base 50°F
3,365
Growing degree days, base 55°F
2,448
Growing degree days, base 60°F
1,648

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,28800
February1,04203
March795137
April4395127
May16458371
June14199635
July2329792
August7275733
September91104466
October38415175
November755027
December1,12402

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 1.2 km from Putnam County. 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 USC00238523 (Unionville). Public domain.