Ice dam risk in New Lenox, IL
Ice dams in New Lenox, IL: how often
8.8 dam days a winter
Moderate risk. On an ordinary house in New Lenox, conditions for an ice dam come on about 8.8 days in a normal winter, mostly in January and February.
New Lenox averages 17 inches of snow a year and about 28 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 New Lenox
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 4.3 | Low |
| Typical, some insulation, not air-sealed | 8.8 | Moderate |
| Older or poorly insulated, warm attic | 14.4 | Moderate |
Sealing and insulating a typical attic takes out about 4.5 days a winter here. It drops the risk from moderate to low. An older house with a warm attic should expect closer to 14.4 days.
What to do about ice dams in New Lenox
- 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.
New Lenox winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 5.0 | 11.6 | 4.2 |
| February | 6.2 | 7.6 | 2.4 |
| March | 2.1 | 2.0 | 0.4 |
| April | 0.1 | 0.0 | 0.0 |
| November | 0.3 | 0.3 | 0.0 |
| December | 3.2 | 6.2 | 1.8 |
New Lenox next to nearby towns
New Lenox ranks 187 of 225 Illinois cities here for ice-dam days, behind Arlington Heights at 21.5 days.
- Mokena, IL 5 mi, 14.7 days
- Frankfort, IL 5 mi, 14.7 days
- Manhattan, IL 6 mi, 8.8 days
- Lockport, IL 6 mi, 12.2 days
- Homer Glen, IL 7 mi, 12.2 days
Where these numbers come from
NOAA 1991–2020 climate normals from Joliet Brandon Rd Dam, 6.9 miles from New Lenox. 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.