Ice dam risk in Shelbyville, IN
Ice dams in Shelbyville, IN: how often
4.0 dam days a winter
Low risk. On an ordinary house in Shelbyville, conditions for an ice dam come on about 4.0 days in a normal winter, mostly in January and February.
Shelbyville averages 15 inches of snow a year and about 15 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 Shelbyville
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 2.4 | Low |
| Typical, some insulation, not air-sealed | 4.0 | Low |
| Older or poorly insulated, warm attic | 6.0 | Moderate |
The attic matters less in Shelbyville than in colder towns: there are only 1.6 days a winter between a typical attic and a sealed one.
Preventing ice dams on a Shelbyville 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.
Shelbyville winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 5.3 | 5.4 | 1.7 |
| February | 3.8 | 4.9 | 1.3 |
| March | 1.8 | 1.2 | 0.2 |
| November | 0.1 | 0.3 | 0.0 |
| December | 3.6 | 3.0 | 0.8 |
Shelbyville next to nearby towns
Shelbyville ranks 80 of 88 Indiana cities here for ice-dam days, behind Plymouth at 15.9 days.
- Franklin, IN 15 mi, 6.0 days
- Greenfield, IN 17 mi, 7.7 days
- Greenwood, IN 18 mi, 6.0 days
- Greensburg, IN 20 mi, 5.7 days
- Beech Grove, IN 20 mi, 7.0 days
Where these numbers come from
NOAA 1991–2020 climate normals from Shelbyville Sewage Plt, 1.5 miles from Shelbyville. 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.