Ice dam risk in Gurnee, IL
How often ice dams form in Gurnee
20.1 dam days a winter
High risk. On an ordinary house in Gurnee, conditions for an ice dam come on about 20.1 days in a normal winter, mostly in January and February.
Gurnee averages 43 inches of snow a year and about 61 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 Gurnee
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 9.3 | Moderate |
| Typical, some insulation, not air-sealed | 20.1 | High |
| Older or poorly insulated, warm attic | 33.6 | High |
Sealing and insulating a typical attic takes out about 10.8 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 33.6 days.
What to do about ice dams in Gurnee
- 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.
Gurnee winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 15.7 | 23.4 | 9.2 |
| February | 8.0 | 15.4 | 4.9 |
| March | 5.8 | 6.5 | 1.4 |
| April | 1.5 | 0.7 | 0.0 |
| October | 0.1 | 0.1 | 0.0 |
| November | 3.1 | 2.7 | 0.4 |
| December | 9.2 | 12.5 | 4.0 |
Gurnee next to nearby towns
Gurnee ranks 8 of 225 Illinois cities here for ice-dam days, behind Arlington Heights at 21.5 days.
- Waukegan, IL 3 mi, 20.1 days
- Grayslake, IL 5 mi, 18.6 days
- North Chicago, IL 5 mi, 18.6 days
- Lindenhurst, IL 6 mi, 20.1 days
- Beach Park, IL 6 mi, 13.7 days
Where these numbers come from
NOAA 1991–2020 climate normals from Lake Villa 2NE, 7.5 miles from Gurnee. 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.