Will Pipes Freeze in Jefferson County, MO? 34 nights a Year
Freeze nights in Jefferson County
In a normal year Jefferson County, MO gets 34 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 50% 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 | 104 nights |
| Bare pipe in garage, attic or outside wall | 20°F | 34 nights |
| Insulated pipe in unheated space | 10°F | 10 nights |
| Inside the heated house | 0°F | 2 nights |
Foam-sleeving a bare pipe in unheated space takes it from 34 nights of risk to 10 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 10/26, last around 04/09. For 20°F: 11/29 to 03/08.
How cold Jefferson County nights get
Average winter (Dec-Feb) low: 25°F; the coldest month, January, averages 22°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: 10 nights a year, and 2 nights below zero.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 22°F | 25°F | 34°F | 44°F | 54°F | 63°F | 67°F | 66°F | 57°F | 46°F | 35°F | 27°F |
Jefferson County next to its neighbours
Washington County, MO, 47 km southwest, gets 39 nights below 20°F to Jefferson County's 34 nights. Monroe County, IL, 32 km east, gets 33 nights.
| County | Distance | Below 32°F | Below 20°F | Jan low |
|---|---|---|---|---|
| Jefferson County, MO | - | 104 nights | 34 nights | 22°F |
| Monroe County, IL | 32 km east | 102 nights | 33 nights | 23°F |
| St. Louis County, MO | 43 km north | 93 nights | 31 nights | 23°F |
| Washington County, MO | 47 km southwest | 105 nights | 39 nights | 21°F |
| Franklin County, MO | 49 km west | 106 nights | 35 nights | 22°F |
| St. Louis city, MO | 49 km northeast | 83 nights | 26 nights | 24°F |
| St. Francois County, MO | 50 km south | 105 nights | 35 nights | 22°F |
Jefferson County within MO
Jefferson County ranks 84 of 115 MO counties for nights below 20°F. The most is Caldwell County, MO at 65 nights, with a 19°F average winter low. The fewest is Pemiscot County, MO: 14 nights, winter lows near 31°F. At 724 ft, Jefferson County sits 118 ft below the state's median county elevation of 842 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.
Why 20°F is the line for a garage pipe: how cold before pipes freeze.
Where this comes from
NOAA 1991-2020 climate normals, blended from 3 nearby stations and adjusted for elevation; closest is Festus, MO, 13 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.