Putnam County climate

Putnam County Frost Dates and Growing Season

NOAA 1991-2020 normals for Hennepin, 7 km from Putnam County, elevation 515 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Hennepin. 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 18 and the first fall freeze around October 22, a growing season of about 188 days.

Median at 36°F
last April 29, first October 12
Median at 32°F
last April 18, first October 22
Median at 28°F
last April 6, first November 1

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

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°F184178173168164160155150143
32°F208201196191188183179173165
28°F231225221215211208203198190
24°F256248243237233228224218211
20°F276268262258253248244238231
16°F294286279274269265260255247

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
5,869
Cooling degree days, base 65°F
946
Growing degree days, base 40°F
5,647
Growing degree days, base 45°F
4,454
Growing degree days, base 50°F
3,387
Growing degree days, base 55°F
2,447
Growing degree days, base 60°F
1,631

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,25400
February1,01903
March775343
April3966142
May14567394
June11207646
July2296759
August6243702
September83107475
October35214186
November718135
December1,10802

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 Putnam 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 USC00114012 (Hennepin). Public domain.