Will Pipes Freeze in Lewis and Clark County, MT? 80 nights a Year
Freeze nights in Lewis and Clark County
In a normal year Lewis and Clark County, MT gets 80 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 82% of US counties.
Risk level: Severe. The risk season runs October to May, worst in December.
It depends where the pipe is
| Pipe | Freezes near | Nights a year |
|---|---|---|
| Outdoor spigot, open crawlspace | 32°F | 189 nights |
| Bare pipe in garage, attic or outside wall | 20°F | 80 nights |
| Insulated pipe in unheated space | 10°F | 42 nights |
| Inside the heated house | 0°F | 22 nights |
Foam-sleeving a bare pipe in unheated space takes it from 80 nights of risk to 42 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 09/15, last around 05/21. For 20°F: 10/19 to 04/19.
How cold Lewis and Clark County nights get
Average winter (Dec-Feb) low: 15°F; the coldest month, January, averages 15°F overnight. 11 months normally bring at least one night below 32°F (Jan, Feb, Mar, Apr, May, Jun, Aug, Sep, Oct, Nov, Dec). Nights below 10°F, cold enough to freeze insulated pipe in an unheated space, come in January, February, March, April, October, November, December: 42 nights a year, and 22 nights below zero.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 15°F | 16°F | 22°F | 28°F | 36°F | 43°F | 47°F | 46°F | 39°F | 31°F | 23°F | 15°F |
Lewis and Clark County next to its neighbours
Powell County, MT, 52 km southwest, gets 126 nights below 20°F to Lewis and Clark County's 80 nights. Cascade County, MT, 81 km east, gets 69 nights.
| County | Distance | Below 32°F | Below 20°F | Jan low |
|---|---|---|---|---|
| Lewis and Clark County, MT | - | 189 nights | 80 nights | 15°F |
| Powell County, MT | 52 km southwest | 241 nights | 126 nights | 9°F |
| Teton County, MT | 78 km north | 177 nights | 83 nights | 13°F |
| Cascade County, MT | 81 km east | 158 nights | 69 nights | 16°F |
| Broadwater County, MT | 111 km southeast | 174 nights | 83 nights | 14°F |
| Granite County, MT | 113 km southwest | 215 nights | 98 nights | 15°F |
| Jefferson County, MT | 114 km south | 214 nights | 107 nights | 10°F |
Lewis and Clark County within MT
Lewis and Clark County ranks 47 of 56 MT counties for nights below 20°F. The most is Sheridan County, MT at 129 nights, with a 2°F average winter low. The fewest is Lake County, MT: 40 nights, winter lows near 22°F. At 5,427 ft, Lewis and Clark County sits 1,505 ft above the state's median county elevation of 3,922 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.
Interior pipes have a threshold too: the four freeze points.
Where this comes from
NOAA 1991-2020 climate normals, blended from 3 nearby stations and adjusted for elevation; closest is Rogers Pass (9 mi NNE), MT, 10 km away (fair match). A normal year, not tonight's forecast: check the forecast low for the night itself. How a county figure is built from stations: how the numbers are made.