Ice dam risk in Baltimore, MD
How often ice dams form in Baltimore
2.7 dam days a winter
Low risk. On an ordinary house in Baltimore, conditions for an ice dam come on about 2.7 days in a normal winter, mostly in February and January.
Baltimore averages 19 inches of snow a year and about 13 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 Baltimore
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 2.1 | Low |
| Typical, some insulation, not air-sealed | 2.7 | Low |
| Older or poorly insulated, warm attic | 3.4 | Low |
The attic matters less in Baltimore than in colder towns: there are only 0.6 days a winter between a typical attic and a sealed one.
Preventing ice dams on a Baltimore 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.
Baltimore winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 6.4 | 4.3 | 1.0 |
| February | 7.5 | 5.2 | 1.1 |
| March | 2.8 | 1.6 | 0.2 |
| November | 0.1 | 0.0 | 0.0 |
| December | 2.5 | 2.0 | 0.4 |
Baltimore next to nearby towns
Baltimore ranks 16 of 23 Maryland cities here for ice-dam days, behind Hagerstown at 12.1 days.
- Laurel, MD 20 mi, 2.9 days
- Bel Air, MD 22 mi, 3.4 days
- Annapolis, MD 23 mi, 3.0 days
- Bowie, MD 25 mi, 3.0 days
- Greenbelt, MD 26 mi, 2.9 days
Where these numbers come from
NOAA 1991–2020 climate normals from Baltimore-Washington International Airport, 9.6 miles from Baltimore. 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.