Ice dam risk in Shorewood, IL

Ice dams in Shorewood, IL: how often

8.8 dam days a winter

Moderate risk. On an ordinary house in Shorewood, conditions for an ice dam come on about 8.8 days in a normal winter, mostly in January and February.

Shorewood 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 Shorewood

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.

Preventing ice dams on a Shorewood 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.

Shorewood 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

Shorewood next to nearby towns

Shorewood ranks 188 of 225 Illinois cities here for ice-dam days, behind Arlington Heights at 21.5 days.

Joliet, IL 3 mi, 8.8 days
Minooka, IL 6 mi, 8.8 days
Crest Hill, IL 7 mi, 12.2 days
Channahon, IL 7 mi, 11.3 days
Plainfield, IL 7 mi, 12.2 days

Where these numbers come from

NOAA 1991–2020 climate normals from Joliet Brandon Rd Dam, 5.9 miles from Shorewood. 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.