Ice dam risk in Alexandria, VA
Will your roof get ice dams in Alexandria, VA?
1.5 dam days a winter
Low risk. On an ordinary house in Alexandria, conditions for an ice dam come on about 1.5 days in a normal winter, mostly in February and January.
Alexandria averages 14 inches of snow a year and about 10 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 Alexandria
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 1.2 | Low |
| Typical, some insulation, not air-sealed | 1.5 | Low |
| Older or poorly insulated, warm attic | 1.9 | Low |
The attic matters less in Alexandria than in colder towns: there are only 0.3 days a winter between a typical attic and a sealed one.
What to do about ice dams in Alexandria
- 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.
Alexandria winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 4.9 | 3.5 | 0.7 |
| February | 5.0 | 4.2 | 0.6 |
| March | 2.0 | 1.2 | 0.1 |
| November | 0.1 | 0.0 | 0.0 |
| December | 1.7 | 1.1 | 0.1 |
Alexandria next to nearby towns
Alexandria ranks 22 of 39 Virginia cities here for ice-dam days, behind Winchester at 4.7 days.
- Falls Church, VA 7 mi, 1.1 days
- Washington, DC 7 mi, 2.1 days
- Vienna, VA 11 mi, 3.7 days
- Fairfax, VA 12 mi, 3.7 days
- Takoma Park, MD 12 mi, 2.1 days
Where these numbers come from
NOAA 1991–2020 climate normals from Washington Reagan Natl Airport, 3.3 miles from Alexandria. 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.