Chilton climate

Chilton Frost Dates and Growing Season

NOAA 1991-2020 normals for Chilton, 1.4 km from Chilton, elevation 840 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Chilton. 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 May 1 and the first fall freeze around October 14, a growing season of about 162 days.

Median at 36°F
last May 14, first October 2
Median at 32°F
last May 1, first October 14
Median at 28°F
last April 22, first October 27

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 28May 23May 20May 17May 14May 11May 7May 3Apr 29
32°FMay 17May 12May 7May 4May 1Apr 29Apr 27Apr 23Apr 19
28°FMay 6May 1Apr 28Apr 25Apr 22Apr 19Apr 15Apr 11Apr 6
24°FApr 25Apr 19Apr 16Apr 12Apr 9Apr 6Apr 4Apr 1Mar 28
20°FApr 14Apr 8Apr 5Apr 3Apr 1Mar 30Mar 27Mar 22Mar 17
16°FApr 6Apr 2Mar 31Mar 27Mar 24Mar 21Mar 17Mar 14Mar 9

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 20Sep 24Sep 27Sep 30Oct 2Oct 5Oct 8Oct 10Oct 15
32°FSep 29Oct 4Oct 7Oct 11Oct 14Oct 16Oct 19Oct 23Oct 30
28°FOct 11Oct 17Oct 21Oct 25Oct 27Oct 30Nov 1Nov 4Nov 8
24°FOct 26Oct 31Nov 1Nov 4Nov 7Nov 10Nov 13Nov 17Nov 21
20°FNov 2Nov 7Nov 10Nov 13Nov 17Nov 20Nov 23Nov 26Dec 1
16°FNov 10Nov 16Nov 20Nov 23Nov 25Nov 28Dec 1Dec 5Dec 10

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°F159153147143139135130126119
32°F183175170165162158154149140
28°F207200195191187182178172165
24°F231223218214210207202197190
20°F251246240235230227222217210
16°F268261256251247244239234227

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
7,552
Cooling degree days, base 65°F
556
Growing degree days, base 40°F
4,419
Growing degree days, base 45°F
3,396
Growing degree days, base 50°F
2,499
Growing degree days, base 55°F
1,723
Growing degree days, base 60°F
1,068

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,46500
February1,23700
March1,034010
April630247
May29327233
June66114499
July13201652
August25155595
September15654356
October502497
November870010
December1,26000

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 1.4 km from Chilton. 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 USC00471568 (Chilton). Public domain.