Ice dam risk in Wilmington, DE
How often ice dams form in Wilmington
3.6 dam days a winter
Low risk. On an ordinary house in Wilmington, conditions for an ice dam come on about 3.6 days in a normal winter, mostly in February and January.
Wilmington averages 12 inches of snow a year and about 17 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 | 2.5 | Low |
| Typical, some insulation, not air-sealed | 3.6 | Low |
| Older or poorly insulated, warm attic | 5.0 | Low |
The attic matters less in Wilmington than in colder towns: there are only 1.1 days a winter between a typical attic and a sealed one.
Preventing ice dams on a Wilmington 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.
Wilmington winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 5.3 | 5.4 | 1.4 |
| February | 4.0 | 6.8 | 1.5 |
| March | 1.8 | 2.6 | 0.3 |
| November | 0.1 | 0.0 | 0.0 |
| December | 0.8 | 2.1 | 0.4 |
Wilmington next to nearby towns
Wilmington ranks 1 of 6 Delaware cities here for ice-dam days, the worst in the state.
- Chester, PA 11 mi, 3.0 days
- Newark, DE 13 mi, 3.5 days
- West Chester, PA 16 mi, 8.5 days
- Elkton, MD 18 mi, 3.5 days
- Darby, PA 19 mi, 3.0 days
Where these numbers come from
NOAA 1991–2020 climate normals from Wilmington Porter Rsch, 2.7 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.