Ice dam risk in Wilmington, OH
How often ice dams form in Wilmington
7.5 dam days a winter
Moderate risk. On an ordinary house in Wilmington, conditions for an ice dam come on about 7.5 days in a normal winter, mostly in January and February.
Wilmington averages 27 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 Wilmington
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 4.3 | Low |
| Typical, some insulation, not air-sealed | 7.5 | Moderate |
| Older or poorly insulated, warm attic | 11.4 | Moderate |
Sealing and insulating a typical attic takes out about 3.2 days a winter here. It drops the risk from moderate to low. An older house with a warm attic should expect closer to 11.4 days.
What to do about ice dams in Wilmington
- 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.
Wilmington winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 8.9 | 11.6 | 3.4 |
| February | 7.4 | 8.8 | 2.2 |
| March | 4.1 | 3.0 | 0.4 |
| April | 0.4 | 0.2 | 0.0 |
| October | 0.1 | 0.0 | 0.0 |
| November | 1.1 | 0.6 | 0.1 |
| December | 4.6 | 5.9 | 1.3 |
Wilmington next to nearby towns
Wilmington ranks 111 of 176 Ohio cities here for ice-dam days, behind Euclid at 24.8 days.
- Xenia, OH 19 mi, 7.5 days
- Lebanon, OH 21 mi, 7.5 days
- Washington Court House, OH 22 mi, 5.6 days
- Centerville, OH 23 mi, 5.7 days
- Springboro, OH 24 mi, 5.7 days
Where these numbers come from
NOAA 1991–2020 climate normals from Wfo Wilmington, 0.6 miles from Wilmington. 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.