Ice dam risk in Highland Park, IL
How often ice dams form in Highland Park
16.1 dam days a winter
High risk. On an ordinary house in Highland Park, conditions for an ice dam come on about 16.1 days in a normal winter, mostly in January and February.
Highland Park averages 34 inches of snow a year and about 53 days with snow on the ground. Most of it comes and goes within a few days. 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 Highland Park
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 8.4 | Moderate |
| Typical, some insulation, not air-sealed | 16.1 | High |
| Older or poorly insulated, warm attic | 25.7 | High |
Sealing and insulating a typical attic takes out about 7.7 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 25.7 days.
What to do about ice dams in Highland Park
- 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.
Highland Park winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 11.3 | 19.5 | 7.0 |
| February | 7.7 | 14.2 | 4.5 |
| March | 5.6 | 6.6 | 1.3 |
| April | 1.1 | 0.6 | 0.0 |
| October | 0.1 | 0.0 | 0.0 |
| November | 1.9 | 1.7 | 0.2 |
| December | 5.9 | 10.4 | 3.0 |
Highland Park next to nearby towns
Highland Park ranks 49 of 225 Illinois cities here for ice-dam days, behind Arlington Heights at 21.5 days.
- Deerfield, IL 2 mi, 16.1 days
- Northbrook, IL 4 mi, 16.1 days
- Lake Forest, IL 4 mi, 16.1 days
- Winnetka, IL 6 mi, 16.1 days
- Wheeling, IL 7 mi, 16.1 days
Where these numbers come from
NOAA 1991–2020 climate normals from Chicago Botanic Garden, 3.2 miles from Highland Park. 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.