Hamilton County climate

Hamilton County Frost Dates and Growing Season

NOAA 1991-2020 normals for Evant 1SSW, 27.4 km from Hamilton County, elevation 1245 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Evant 1SSW. 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 15 and the first fall freeze around November 18, a growing season of about 247 days.

Median at 36°F
last March 29, first November 6
Median at 32°F
last March 15, first November 18
Median at 28°F
last March 2, first November 30

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

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

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°F250240233228224220215209201
32°F271263258253247242236230222
28°F302291283276271266261254245
24°F338326317310303296289280269
20°F365365353345336329319307294
16°F365365365365365363351340326

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
99% of years
20°F or colder
84% of years
16°F or colder
45% 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
2,285
Cooling degree days, base 65°F
2,499
Growing degree days, base 40°F
9,458
Growing degree days, base 45°F
7,782
Growing degree days, base 50°F
6,227
Growing degree days, base 55°F
4,822
Growing degree days, base 60°F
3,579

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January586269
February4264101
March28022252
April9185449
May13247699
June0456906
July05571,022
August05841,049
September5371816
October70146545
November28924231
December524389

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 27.4 km from Hamilton 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 USC00413005 (Evant 1SSW). Public domain.