Madison County climate

Madison County Frost Dates and Growing Season

NOAA 1991-2020 normals for Norfolk Karl Stefan AP, 15.7 km from Madison County, elevation 1551 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Norfolk Karl Stefan AP. 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 30 and the first fall freeze around October 5, a growing season of about 157 days.

Median at 36°F
last May 9, first September 28
Median at 32°F
last April 30, first October 5
Median at 28°F
last April 20, first October 16

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 23May 19May 15May 12May 9May 7May 4May 1Apr 27
32°FMay 14May 9May 6May 3Apr 30Apr 27Apr 24Apr 21Apr 16
28°FMay 5Apr 30Apr 26Apr 23Apr 20Apr 17Apr 13Apr 10Apr 6
24°FApr 23Apr 19Apr 15Apr 12Apr 9Apr 6Apr 3Mar 31Mar 26
20°FApr 15Apr 9Apr 6Apr 3Mar 31Mar 28Mar 24Mar 19Mar 13
16°FApr 6Apr 1Mar 29Mar 25Mar 22Mar 17Mar 13Mar 9Mar 4

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 14Sep 19Sep 21Sep 24Sep 28Sep 30Oct 2Oct 5Oct 10
32°FSep 21Sep 26Sep 30Oct 2Oct 5Oct 7Oct 10Oct 14Oct 18
28°FSep 30Oct 5Oct 9Oct 13Oct 16Oct 19Oct 21Oct 24Oct 28
24°FOct 11Oct 17Oct 21Oct 23Oct 26Oct 28Oct 31Nov 3Nov 7
20°FOct 22Oct 26Oct 29Nov 1Nov 3Nov 6Nov 9Nov 12Nov 17
16°FOct 30Nov 2Nov 6Nov 8Nov 11Nov 14Nov 17Nov 21Nov 27

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°F157152147143139135132128120
32°F176169165161157154150144138
28°F198191186181177173168164157
24°F218211206202197193189185178
20°F238231225220217213209204195
16°F257249244240235230225221214

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
6,623
Cooling degree days, base 65°F
907
Growing degree days, base 40°F
5,250
Growing degree days, base 45°F
4,127
Growing degree days, base 50°F
3,133
Growing degree days, base 55°F
2,263
Growing degree days, base 60°F
1,519

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,32500
February1,08302
March844128
April4887104
May20654330
June29191612
July4308769
August11240694
September11696436
October44910140
November848018
December1,22000

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 15.7 km from Madison 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 USW00014941 (Norfolk Karl Stefan AP). Public domain.