Ice dam risk in Centralia, IL
Ice dams in Centralia, IL: how often
4.1 dam days a winter
Low risk. On an ordinary house in Centralia, conditions for an ice dam come on about 4.1 days in a normal winter, mostly in January and February.
Centralia averages 12 inches of snow a year and about 16 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 Centralia
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 2.6 | Low |
| Typical, some insulation, not air-sealed | 4.1 | Low |
| Older or poorly insulated, warm attic | 5.9 | Moderate |
The attic matters less in Centralia than in colder towns: there are only 1.5 days a winter between a typical attic and a sealed one.
Preventing ice dams on a Centralia roof
- Check the gutters before the first snow and clear them, so meltwater has somewhere to go. If you see icicles thicker than a finger along the eave after a storm, that is the early sign to look at the attic.
Snowy places are not always the worst: why snowfall misleads.
Centralia winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 3.4 | 5.7 | 1.6 |
| February | 4.5 | 4.9 | 1.2 |
| March | 0.5 | 0.8 | 0.1 |
| November | 0.4 | 0.3 | 0.0 |
| December | 3.2 | 4.4 | 1.1 |
Centralia next to nearby towns
Centralia ranks 204 of 225 Illinois cities here for ice-dam days, behind Arlington Heights at 21.5 days.
- Mount Vernon, IL 18 mi, 2.8 days
- Highland, IL 35 mi, 2.5 days
- Shiloh, IL 43 mi, 2.5 days
- O'Fallon, IL 43 mi, 2.5 days
- Troy, IL 44 mi, 2.5 days
Where these numbers come from
NOAA 1991–2020 climate normals from Iuka 12 SW, 8.5 miles from Centralia. 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.