Will Pipes Freeze in Johnson County, IA? 62 nights a Year
Freeze nights in Johnson County
In a normal year Johnson County, IA 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 | 134 nights |
| Bare pipe in garage, attic or outside wall | 20°F | 62 nights |
| Insulated pipe in unheated space | 10°F | 30 nights |
| Inside the heated house | 0°F | 11 nights |
Foam-sleeving a bare pipe in unheated space takes it from 62 nights of risk to 30 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 10/18, last around 04/21. For 20°F: 11/17 to 03/18.
How cold Johnson 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: 30 nights a year, and 11 nights below zero.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 14°F | 18°F | 29°F | 39°F | 51°F | 61°F | 65°F | 62°F | 53°F | 41°F | 30°F | 19°F |
Johnson County next to its neighbours
Iowa County, IA, 39 km west, gets 74 nights below 20°F to Johnson County's 62 nights. Muscatine County, IA, 44 km southeast, gets 57 nights.
| County | Distance | Below 32°F | Below 20°F | Jan low |
|---|---|---|---|---|
| Johnson County, IA | - | 134 nights | 62 nights | 14°F |
| Iowa County, IA | 39 km west | 151 nights | 74 nights | 10°F |
| Washington County, IA | 40 km south | 139 nights | 65 nights | 12°F |
| Cedar County, IA | 40 km east | 150 nights | 74 nights | 12°F |
| Muscatine County, IA | 44 km southeast | 126 nights | 57 nights | 14°F |
| Linn County, IA | 45 km north | 135 nights | 63 nights | 12°F |
| Louisa County, IA | 57 km southeast | 131 nights | 57 nights | 12°F |
Johnson County within IA
Johnson County ranks 89 of 99 IA counties for nights below 20°F. The most is Osceola County, IA at 99 nights, with a 8°F average winter low. The fewest is Des Moines County, IA: 52 nights, winter lows near 19°F. At 711 ft, Johnson County sits 379 ft below the state's median county elevation of 1,090 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 Iowa City Municipal Airport, IA, 6 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.