Ice dam risk in Merrillville, IN
How often ice dams form in Merrillville
11.9 dam days a winter
Moderate risk. On an ordinary house in Merrillville, conditions for an ice dam come on about 11.9 days in a normal winter, mostly in January and February.
Merrillville averages 40 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 Merrillville
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 5.7 | Moderate |
| Typical, some insulation, not air-sealed | 11.9 | Moderate |
| Older or poorly insulated, warm attic | 19.5 | High |
Sealing and insulating a typical attic takes out about 6.1 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 19.5 days.
Preventing ice dams on a Merrillville 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.
Merrillville winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 14.6 | 14.7 | 5.4 |
| February | 5.5 | 10.9 | 3.1 |
| March | 6.7 | 3.6 | 0.7 |
| April | 1.2 | 0.3 | 0.0 |
| October | 0.3 | 0.0 | 0.0 |
| November | 2.3 | 0.6 | 0.1 |
| December | 9.4 | 8.5 | 2.5 |
Merrillville next to nearby towns
Merrillville ranks 31 of 88 Indiana cities here for ice-dam days, behind Plymouth at 15.9 days.
- Hobart, IN 4 mi, 14.0 days
- Crown Point, IN 5 mi, 12.2 days
- Schererville, IN 7 mi, 14.7 days
- Griffith, IN 7 mi, 14.7 days
- Lake Station, IN 8 mi, 14.1 days
Where these numbers come from
NOAA 1991–2020 climate normals from Valparaiso Wtr Wks, 14.7 miles from Merrillville. 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.
- Snow-on-the-ground counts come from a second, nearby station, because the closest one does not record them.