Will Pipes Freeze in St. Louis County, MO? 31 nights a Year
Freeze nights in St. Louis County
In a normal year St. Louis County, MO gets 31 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 47% 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 | 93 nights |
| Bare pipe in garage, attic or outside wall | 20°F | 31 nights |
| Insulated pipe in unheated space | 10°F | 9 nights |
| Inside the heated house | 0°F | 2 nights |
Foam-sleeving a bare pipe in unheated space takes it from 31 nights of risk to 9 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 10/29, last around 04/04. For 20°F: 12/01 to 03/05.
How cold St. Louis County nights get
Average winter (Dec-Feb) low: 26°F; the coldest month, January, averages 23°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: 9 nights a year, and 2 nights below zero.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 23°F | 27°F | 36°F | 47°F | 57°F | 66°F | 70°F | 69°F | 60°F | 48°F | 37°F | 28°F |
St. Louis County next to its neighbours
St. Charles County, MO, 25 km northwest, gets 37 nights below 20°F to St. Louis County's 31 nights. St. Louis city, MO, 18 km east, gets 26 nights.
| County | Distance | Below 32°F | Below 20°F | Jan low |
|---|---|---|---|---|
| St. Louis County, MO | - | 93 nights | 31 nights | 23°F |
| St. Louis city, MO | 18 km east | 83 nights | 26 nights | 24°F |
| St. Charles County, MO | 25 km northwest | 104 nights | 37 nights | 21°F |
| Jefferson County, MO | 43 km south | 104 nights | 34 nights | 22°F |
| Monroe County, IL | 47 km southeast | 102 nights | 33 nights | 23°F |
| St. Clair County, IL | 49 km southeast | 94 nights | 28 nights | 24°F |
| Jersey County, IL | 49 km north | 117 nights | 42 nights | 19°F |
St. Louis County within MO
St. Louis County ranks 96 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 645 ft, St. Louis County sits 197 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.
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 St Charles (7 mi SSW), MO, 8 km away (close match). A normal year, not tonight's forecast: check the forecast low for the night itself. What a "fair" or "distant" station match means is in the method guide.