Ice dam risk in Whitewater, WI
Ice dams in Whitewater, WI: how often
21.9 dam days a winter
High risk. On an ordinary house in Whitewater, conditions for an ice dam come on about 21.9 days in a normal winter, mostly in January and February.
Whitewater averages 34 inches of snow a year and about 62 days with snow on the ground. Snow that lies that long is what turns a little attic heat into a ridge of ice at the eave. The conditions that make a dam need all three at once: snow, cold at the eave and heat above it.
What your attic does to that number in Whitewater
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 9.5 | Moderate |
| Typical, some insulation, not air-sealed | 21.9 | High |
| Older or poorly insulated, warm attic | 37.3 | Severe |
Sealing and insulating a typical attic takes out about 12.3 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 37.3 days.
What to do about ice dams in Whitewater
- Air-seal the attic floor: the gaps around the hatch, light fixtures, plumbing stacks and the top plates of interior walls. This is the fix that removes the cause, and it usually costs less than a season of contractor ice removal.
- Rake the bottom three or four feet of roof after any storm that leaves more than about six inches, from the ground with a roof rake.
- At the next reroof, ask for ice-and-water membrane under the shingles from the eave to at least 24 inches inside the wall line. It does not stop a dam; it stops the leak when one forms.
Which to spend on first: air sealing or heat cable.
Whitewater winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 8.5 | 21.1 | 8.6 |
| February | 9.9 | 18.5 | 6.8 |
| March | 4.4 | 7.7 | 1.9 |
| April | 0.7 | 0.7 | 0.1 |
| May | 0.1 | 0.0 | 0.0 |
| October | 0.1 | 0.1 | 0.0 |
| November | 1.2 | 1.8 | 0.4 |
| December | 9.0 | 12.2 | 4.2 |
Whitewater next to nearby towns
Whitewater ranks 67 of 98 Wisconsin cities here for ice-dam days, behind Wausau at 41.6 days.
- Fort Atkinson, WI 8 mi, 22.2 days
- Elkhorn, WI 15 mi, 19.2 days
- Janesville, WI 18 mi, 20.5 days
- Oconomowoc, WI 22 mi, 22.2 days
- Watertown, WI 24 mi, 22.3 days
Where these numbers come from
NOAA 1991–2020 climate normals from Whitewater Wwtp, 1.0 miles from Whitewater. A dam day is a day with snow on the roof and freezing at the eave while heat or sun melts the snow above it. This describes a normal winter, not this one.