McHenry County climate

McHenry County Frost Dates and Growing Season

NOAA 1991-2020 normals for Towner 2 Ne, 23.6 km from McHenry County, elevation 1480 ft

Frost and the growing season

NOAA's 1991-2020 freeze probabilities for Towner 2 Ne. 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 17 and the first fall freeze around September 22, a growing season of about 126 days.

Median at 36°F
last May 28, first September 13
Median at 32°F
last May 17, first September 22
Median at 28°F
last May 8, first October 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°FJun 10Jun 4Jun 1May 30May 28May 25May 23May 19May 15
32°FJun 1May 28May 24May 20May 17May 15May 12May 9May 5
28°FMay 22May 16May 13May 10May 8May 5May 3Apr 30Apr 25
24°FMay 12May 7May 3May 1Apr 29Apr 25Apr 22Apr 17Apr 12
20°FMay 2Apr 29Apr 24Apr 20Apr 17Apr 14Apr 11Apr 8Apr 4
16°FApr 25Apr 19Apr 15Apr 12Apr 9Apr 7Apr 4Apr 2Mar 29

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 1Sep 5Sep 8Sep 11Sep 13Sep 16Sep 18Sep 21Sep 25
32°FSep 10Sep 15Sep 18Sep 20Sep 22Sep 24Sep 27Sep 30Oct 3
28°FSep 19Sep 24Sep 26Sep 29Oct 1Oct 3Oct 5Oct 8Oct 12
24°FSep 29Oct 1Oct 4Oct 7Oct 9Oct 11Oct 14Oct 17Oct 21
20°FOct 3Oct 7Oct 11Oct 14Oct 18Oct 20Oct 23Oct 26Oct 31
16°FOct 11Oct 17Oct 21Oct 24Oct 27Oct 30Nov 1Nov 4Nov 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°F1251201151121081051009588
32°F144138134130126122118113108
28°F163157153149145141138133126
24°F184178172168163160156152145
20°F200195190186182177173168161
16°F216210205202198194190184177

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
9,510
Cooling degree days, base 65°F
390
Growing degree days, base 40°F
3,815
Growing degree days, base 45°F
2,898
Growing degree days, base 50°F
2,087
Growing degree days, base 55°F
1,390
Growing degree days, base 60°F
817

Growing degree days by month, base 50°F

Heating and cooling by month

MonthHeating DDCooling DDGrowing DD 50
January1,79000
February1,50800
March1,26501
April730130
May35113186
June9860414
July26156595
August44132553
September24928259
October683147
November1,15801
December1,61000

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 23.6 km from McHenry 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 USC00328792 (Towner 2 Ne). Public domain.