Ice dam risk in Blacksburg, VA
How often ice dams form in Blacksburg
4.5 dam days a winter
Low risk. On an ordinary house in Blacksburg, conditions for an ice dam come on about 4.5 days in a normal winter, mostly in January and February.
Blacksburg averages 25 inches of snow a year and about 19 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 Blacksburg
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 3.4 | Low |
| Typical, some insulation, not air-sealed | 4.5 | Low |
| Older or poorly insulated, warm attic | 5.8 | Moderate |
The attic matters less in Blacksburg than in colder towns: there are only 1.1 days a winter between a typical attic and a sealed one.
What to do about ice dams in Blacksburg
- 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.
Blacksburg winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 7.7 | 6.1 | 1.6 |
| February | 7.0 | 5.9 | 1.4 |
| March | 4.3 | 2.6 | 0.4 |
| April | 0.6 | 0.2 | 0.0 |
| November | 0.4 | 0.1 | 0.0 |
| December | 4.7 | 4.3 | 1.0 |
Blacksburg next to nearby towns
Blacksburg ranks 2 of 39 Virginia cities here for ice-dam days, behind Winchester at 4.7 days.
- Christiansburg, VA 6 mi, 4.3 days
- Radford, VA 11 mi, 4.3 days
- Salem, VA 21 mi, 1.7 days
- Roanoke, VA 26 mi, 1.7 days
- Martinsville, VA 49 mi, 0.5 days
Where these numbers come from
NOAA 1991–2020 climate normals from Blacksburg Nwso, 2.0 miles from Blacksburg. 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.