Ice dam risk in Rantoul, IL
Ice dams in Rantoul, IL: how often
9.6 dam days a winter
Moderate risk. On an ordinary house in Rantoul, conditions for an ice dam come on about 9.6 days in a normal winter, mostly in January and February.
Rantoul averages 18 inches of snow a year and about 30 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 Rantoul
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 4.8 | Low |
| Typical, some insulation, not air-sealed | 9.6 | Moderate |
| Older or poorly insulated, warm attic | 15.5 | High |
Sealing and insulating a typical attic takes out about 4.8 days a winter here. It drops the risk from moderate to low. An older house with a warm attic should expect closer to 15.5 days.
Preventing ice dams on a Rantoul 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.
Which to spend on first: air sealing or heat cable.
Rantoul winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 4.9 | 12.2 | 4.4 |
| February | 6.1 | 8.9 | 2.8 |
| March | 2.1 | 2.2 | 0.4 |
| April | 0.3 | 0.2 | 0.0 |
| November | 0.7 | 0.9 | 0.2 |
| December | 4.2 | 6.0 | 1.8 |
Rantoul next to nearby towns
Rantoul ranks 181 of 225 Illinois cities here for ice-dam days, behind Arlington Heights at 21.5 days.
- Urbana, IL 13 mi, 8.8 days
- Champaign, IL 14 mi, 8.8 days
- Mahomet, IL 15 mi, 8.8 days
- Danville, IL 31 mi, 7.7 days
- Bloomington, IL 45 mi, 9.8 days
Where these numbers come from
NOAA 1991–2020 climate normals from Paxton 2 WSW, 10.6 miles from Rantoul. 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.