Will Pipes Freeze in Jefferson County, MT? 107 nights a Year
Freeze nights in Jefferson County
In a normal year Jefferson County, MT gets 107 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 94% 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 | 214 nights |
| Bare pipe in garage, attic or outside wall | 20°F | 107 nights |
| Insulated pipe in unheated space | 10°F | 56 nights |
| Inside the heated house | 0°F | 26 nights |
Foam-sleeving a bare pipe in unheated space takes it from 107 nights of risk to 56 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 09/08, last around 06/07. For 20°F: 10/09 to 04/27.
How cold Jefferson County nights get
Average winter (Dec-Feb) low: 11°F; the coldest month, December, averages 10°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: 56 nights a year, and 26 nights below zero.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 10°F | 12°F | 20°F | 26°F | 34°F | 41°F | 47°F | 45°F | 37°F | 27°F | 18°F | 10°F |
Jefferson County next to its neighbours
Silver Bow County, MT, 53 km southwest, gets 127 nights below 20°F to Jefferson County's 107 nights. Broadwater County, MT, 49 km northeast, gets 83 nights.
| County | Distance | Below 32°F | Below 20°F | Jan low |
|---|---|---|---|---|
| Jefferson County, MT | - | 214 nights | 107 nights | 10°F |
| Broadwater County, MT | 49 km northeast | 174 nights | 83 nights | 14°F |
| Silver Bow County, MT | 53 km southwest | 235 nights | 127 nights | 9°F |
| Deer Lodge County, MT | 83 km west | 230 nights | 113 nights | 13°F |
| Madison County, MT | 90 km south | 213 nights | 107 nights | 13°F |
| Gallatin County, MT | 97 km southeast | 233 nights | 123 nights | 11°F |
| Meagher County, MT | 101 km northeast | 204 nights | 95 nights | 13°F |
Jefferson County within MT
Jefferson County ranks 13 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 7,167 ft, Jefferson County sits 3,244 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 Boulder, MT, 13 km away (distant 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.