Ice dam risk in Des Plaines, IL
How often ice dams form in Des Plaines
13.3 dam days a winter
Moderate risk. On an ordinary house in Des Plaines, conditions for an ice dam come on about 13.3 days in a normal winter, mostly in January and February.
Des Plaines averages 38 inches of snow a year and about 44 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 Des Plaines
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 6.5 | Moderate |
| Typical, some insulation, not air-sealed | 13.3 | Moderate |
| Older or poorly insulated, warm attic | 21.7 | High |
Sealing and insulating a typical attic takes out about 6.8 days a winter here. It does not move the risk band, but it shortens every dam. An older house with a warm attic should expect closer to 21.7 days.
Preventing ice dams on a Des Plaines 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.
Which to spend on first: air sealing or heat cable.
Des Plaines winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 11.3 | 16.1 | 5.8 |
| February | 10.7 | 11.9 | 3.7 |
| March | 5.5 | 4.6 | 0.8 |
| April | 1.3 | 0.5 | 0.0 |
| October | 0.2 | 0.0 | 0.0 |
| November | 1.8 | 1.3 | 0.2 |
| December | 7.6 | 9.2 | 2.7 |
Des Plaines next to nearby towns
Des Plaines ranks 97 of 225 Illinois cities here for ice-dam days, behind Arlington Heights at 21.5 days.
- Mount Prospect, IL 3 mi, 13.3 days
- Park Ridge, IL 3 mi, 13.3 days
- Niles, IL 5 mi, 13.3 days
- Prospect Heights, IL 5 mi, 16.1 days
- Elk Grove Village, IL 5 mi, 13.3 days
Where these numbers come from
NOAA 1991–2020 climate normals from Chicago Ohare International Airport, 5.4 miles from Des Plaines. 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.