Will Pipes Freeze in Johnson County, IL? 23 nights a Year
Freeze nights in Johnson County
In a normal year Johnson County, IL gets 23 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 39% of US counties.
Risk level: Regular. The risk season runs November to March, worst in January.
It depends where the pipe is
| Pipe | Freezes near | Nights a year |
|---|---|---|
| Outdoor spigot, open crawlspace | 32°F | 83 nights |
| Bare pipe in garage, attic or outside wall | 20°F | 23 nights |
| Insulated pipe in unheated space | 10°F | 6 nights |
| Inside the heated house | 0°F | under 1 night |
Foam-sleeving a bare pipe in unheated space takes it from 23 nights of risk to 6 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 10/21, last around 04/14. For 20°F: 11/23 to 03/07.
How cold Johnson County nights get
Average winter (Dec-Feb) low: 28°F; the coldest month, January, averages 26°F overnight. 7 months normally bring at least one night below 32°F (Jan, Feb, Mar, Apr, Oct, Nov, Dec). Nights below 10°F, cold enough to freeze insulated pipe in an unheated space, come in January, February, December: 6 nights a year, and under 1 night below zero.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 26°F | 29°F | 37°F | 46°F | 56°F | 64°F | 67°F | 66°F | 58°F | 47°F | 37°F | 30°F |
Johnson County next to its neighbours
Williamson County, IL, 30 km north, gets 29 nights below 20°F to Johnson County's 23 nights. Massac County, IL, 31 km southeast, gets 22 nights.
| County | Distance | Below 32°F | Below 20°F | Jan low |
|---|---|---|---|---|
| Johnson County, IL | - | 83 nights | 23 nights | 26°F |
| Williamson County, IL | 30 km north | 98 nights | 29 nights | 24°F |
| Pope County, IL | 30 km east | 90 nights | 27 nights | 25°F |
| Massac County, IL | 31 km southeast | 83 nights | 22 nights | 26°F |
| Union County, IL | 32 km west | 95 nights | 28 nights | 25°F |
| Pulaski County, IL | 35 km southwest | 81 nights | 23 nights | 26°F |
| Saline County, IL | 44 km northeast | 95 nights | 25 nights | 24°F |
Johnson County within IL
Johnson County ranks 98 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 519 ft, Johnson County sits 113 ft below the state's median county elevation of 632 ft.
What to do here
- Insulate every pipe in unheated space before the season starts.
- Heat tape on the runs you cannot insulate well.
- Shut off and drain outdoor spigots for the season.
When to have the house ready: when freeze season starts.
Where this comes from
NOAA 1991-2020 climate normals, blended from 3 nearby stations and adjusted for elevation; closest is Dixon Springs Agric Ctr, IL, 19 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.