Ice dam risk in Crest Hill, IL
How often ice dams form in Crest Hill
12.2 dam days a winter
Moderate risk. On an ordinary house in Crest Hill, conditions for an ice dam come on about 12.2 days in a normal winter, mostly in January and February.
Crest Hill averages 33 inches of snow a year and about 39 days with snow on the ground. Plenty falls, but it tends to melt off between storms, which keeps the count lower than the snowfall suggests. That gap is why snowfall alone misleads.
What your attic does to that number in Crest Hill
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 6.0 | Moderate |
| Typical, some insulation, not air-sealed | 12.2 | Moderate |
| Older or poorly insulated, warm attic | 20.0 | High |
Sealing and insulating a typical attic takes out about 6.2 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 20.0 days.
Preventing ice dams on a Crest Hill 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.
Crest Hill winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 10.6 | 14.9 | 5.3 |
| February | 8.7 | 11.1 | 3.5 |
| March | 4.2 | 3.2 | 0.6 |
| April | 0.9 | 0.2 | 0.0 |
| October | 0.1 | 0.0 | 0.0 |
| November | 1.2 | 1.0 | 0.1 |
| December | 7.5 | 8.8 | 2.7 |
Crest Hill next to nearby towns
Crest Hill ranks 152 of 225 Illinois cities here for ice-dam days, behind Arlington Heights at 21.5 days.
- Romeoville, IL 4 mi, 12.2 days
- Joliet, IL 4 mi, 8.8 days
- Lockport, IL 4 mi, 12.2 days
- Shorewood, IL 7 mi, 8.8 days
- Plainfield, IL 7 mi, 12.2 days
Where these numbers come from
NOAA 1991–2020 climate normals from Romeoville Wfo, 2.5 miles from Crest Hill. 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.