Will Pipes Freeze in Dewey County, SD? 94 nights a Year
Freeze nights in Dewey County
In a normal year Dewey County, SD gets 94 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 89% of US counties.
Risk level: Severe. The risk season runs October to April, worst in January.
It depends where the pipe is
| Pipe | Freezes near | Nights a year |
|---|---|---|
| Outdoor spigot, open crawlspace | 32°F | 170 nights |
| Bare pipe in garage, attic or outside wall | 20°F | 94 nights |
| Insulated pipe in unheated space | 10°F | 52 nights |
| Inside the heated house | 0°F | 26 nights |
Foam-sleeving a bare pipe in unheated space takes it from 94 nights of risk to 52 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 09/30, last around 05/10. For 20°F: 10/26 to 04/10.
How cold Dewey County nights get
Average winter (Dec-Feb) low: 11°F; the coldest month, January, averages 8°F overnight. 9 months normally bring at least one night below 32°F (Jan, Feb, Mar, Apr, May, Sep, Oct, Nov, Dec). Nights below 10°F, cold enough to freeze insulated pipe in an unheated space, come in January, February, March, April, November, December: 52 nights a year, and 26 nights below zero.
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 8°F | 11°F | 22°F | 32°F | 44°F | 54°F | 60°F | 58°F | 49°F | 35°F | 22°F | 13°F |
Dewey County next to its neighbours
Corson County, SD, 65 km northwest, gets 101 nights below 20°F to Dewey County's 94 nights. Ziebach County, SD, 67 km west, gets 91 nights.
| County | Distance | Below 32°F | Below 20°F | Jan low |
|---|---|---|---|---|
| Dewey County, SD | - | 170 nights | 94 nights | 8°F |
| Corson County, SD | 65 km northwest | 177 nights | 101 nights | 6°F |
| Ziebach County, SD | 67 km west | 171 nights | 91 nights | 10°F |
| Potter County, SD | 70 km east | 176 nights | 105 nights | 5°F |
| Walworth County, SD | 71 km northeast | 178 nights | 105 nights | 4°F |
| Sully County, SD | 73 km southeast | 172 nights | 99 nights | 7°F |
| Stanley County, SD | 82 km south | 167 nights | 94 nights | 8°F |
Dewey County within SD
Dewey County ranks 38 of 66 SD counties for nights below 20°F. The most is Codington County, SD at 113 nights, with a 6°F average winter low. The fewest is Tripp County, SD: 75 nights, winter lows near 15°F. At 2,271 ft, Dewey County sits 486 ft above the state's median county elevation of 1,785 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 Timber Lake, SD, 36 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.