Ice dam risk in Hudson, WI
Will your roof get ice dams in Hudson, WI?
38.8 dam days a winter
Severe risk. On an ordinary house in Hudson, conditions for an ice dam come on about 38.8 days in a normal winter, mostly in January and February.
Hudson averages 43 inches of snow a year and about 101 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 Hudson
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 14.2 | Moderate |
| Typical, some insulation, not air-sealed | 38.8 | Severe |
| Older or poorly insulated, warm attic | 69.6 | Severe |
Sealing and insulating a typical attic takes out about 24.6 days a winter here. It drops the risk from severe to moderate. An older house with a warm attic should expect closer to 69.6 days.
Preventing ice dams on a Hudson roof
- 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.
Hudson winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 9.4 | 27.3 | 12.2 |
| February | 8.0 | 26.4 | 11.3 |
| March | 8.3 | 18.3 | 5.1 |
| April | 3.3 | 3.0 | 0.5 |
| May | 0.5 | 0.1 | 0.0 |
| October | 0.4 | 0.4 | 0.0 |
| November | 4.1 | 4.8 | 1.3 |
| December | 9.4 | 20.6 | 8.4 |
Hudson next to nearby towns
Hudson ranks 4 of 98 Wisconsin cities here for ice-dam days, behind Wausau at 41.6 days.
- Stillwater, MN 8 mi, 22.8 days
- River Falls, WI 9 mi, 38.8 days
- Lake Elmo, MN 9 mi, 22.8 days
- Woodbury, MN 10 mi, 22.8 days
- Oakdale, MN 12 mi, 22.8 days
Where these numbers come from
NOAA 1991–2020 climate normals from Baldwin, 16.6 miles from Hudson. 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.