Will Pipes Freeze in McHenry County, IL? 62 nights a Year
Freeze nights in McHenry County
In a normal year McHenry County, IL gets 62 nights at or below 20°F, the point where bare pipes in a garage, attic or outside wall start to freeze. That is more than 72% of US counties.
Risk level: Severe. The risk season runs November to April, worst in January.
It depends where the pipe is
| Pipe | Freezes near | Nights a year |
|---|---|---|
| Outdoor spigot, open crawlspace | 32°F | 139 nights |
| Bare pipe in garage, attic or outside wall | 20°F | 62 nights |
| Insulated pipe in unheated space | 10°F | 31 nights |
| Inside the heated house | 0°F | 14 nights |
Foam-sleeving a bare pipe in unheated space takes it from 62 nights of risk to 31 nights. A 12 ft heat-tape kit runs $17 to $37; an average burst-pipe repair is about $500.
Month by month
Nights at or below 20°F in a normal year.
First 32°F night is usually around 10/22, last around 04/25. For 20°F: 11/21 to 03/21.
How cold McHenry County nights get
Average winter (Dec-Feb) low: 17°F; the coldest month, January, averages 14°F overnight. 8 months normally bring at least one night below 32°F (Jan, Feb, Mar, Apr, May, Oct, Nov, Dec). Nights below 10°F, cold enough to freeze insulated pipe in an unheated space, come in January, February, March, November, December: 31 nights a year, and 14 nights below zero.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 14°F | 16°F | 26°F | 37°F | 48°F | 58°F | 62°F | 61°F | 52°F | 42°F | 30°F | 20°F |
McHenry County next to its neighbours
Boone County, IL, 31 km west, gets 70 nights below 20°F to McHenry County's 62 nights. Walworth County, WI, 39 km north, gets 61 nights.
| County | Distance | Below 32°F | Below 20°F | Jan low |
|---|---|---|---|---|
| McHenry County, IL | - | 139 nights | 62 nights | 14°F |
| Boone County, IL | 31 km west | 146 nights | 70 nights | 12°F |
| Walworth County, WI | 39 km north | 141 nights | 61 nights | 14°F |
| Kane County, IL | 43 km south | 138 nights | 61 nights | 15°F |
| DeKalb County, IL | 54 km southwest | 141 nights | 64 nights | 13°F |
| Kenosha County, WI | 55 km northeast | 133 nights | 59 nights | 16°F |
| Lake County, IL | 55 km east | 127 nights | 53 nights | 17°F |
McHenry County within IL
McHenry County ranks 12 of 102 IL counties for nights below 20°F. The most is Jo Daviess County, IL at 76 nights, with a 14°F average winter low. The fewest is Alexander County, IL: 21 nights, winter lows near 29°F. At 905 ft, McHenry County sits 273 ft above the state's median county elevation of 632 ft.
What to do here
- Treat it as a building fix, not a night-of routine: insulate, heat tape, seal crawlspace vents.
- An automatic leak shutoff pays for itself if one burst is avoided.
- Know where the main shutoff is before the first hard freeze.
At this many nights, foam alone is not the answer: insulate or heat tape?.
Where this comes from
NOAA 1991-2020 climate normals, blended from 3 nearby stations and adjusted for elevation; closest is Crystal Lake (4 mi NW), IL, 8 km away (close match). A normal year, not tonight's forecast: check the forecast low for the night itself. Why elevation is part of the blend: how county numbers are made.