Ice dam risk in Owosso, MI
How often ice dams form in Owosso
22.5 dam days a winter
High risk. On an ordinary house in Owosso, conditions for an ice dam come on about 22.5 days in a normal winter, mostly in January and February.
Owosso averages 38 inches of snow a year and about 67 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 Owosso
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 10.5 | Moderate |
| Typical, some insulation, not air-sealed | 22.5 | High |
| Older or poorly insulated, warm attic | 37.4 | Severe |
Sealing and insulating a typical attic takes out about 12.0 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 37.4 days.
Preventing ice dams on a Owosso 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.
Owosso winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 12.4 | 22.8 | 8.8 |
| February | 8.9 | 19.1 | 6.8 |
| March | 4.0 | 8.9 | 2.2 |
| April | 0.8 | 0.5 | 0.1 |
| October | 0.2 | 0.1 | 0.0 |
| November | 2.1 | 1.9 | 0.3 |
| December | 9.9 | 13.5 | 4.2 |
Owosso next to nearby towns
Owosso ranks 9 of 90 Michigan cities here for ice-dam days, behind Sault Ste. Marie at 48.8 days.
- East Lansing, MI 23 mi, 21.3 days
- Flint, MI 25 mi, 19.5 days
- Fenton, MI 27 mi, 21.4 days
- Lansing, MI 28 mi, 21.6 days
- Burton, MI 28 mi, 21.4 days
Where these numbers come from
NOAA 1991–2020 climate normals from Owosso Wwtp, 1.5 miles from Owosso. 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.