Ice dam risk in Frederick, MD
Will your roof get ice dams in Frederick, MD?
5.8 dam days a winter
Moderate risk. On an ordinary house in Frederick, conditions for an ice dam come on about 5.8 days in a normal winter, mostly in February and January.
Frederick averages 31 inches of snow a year and about 26 days with snow on the ground. Plenty falls, but it tends to melt off between storms, which keeps the count lower than the snowfall suggests. That gap is why snowfall alone misleads.
What your attic does to that number in Frederick
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 3.8 | Low |
| Typical, some insulation, not air-sealed | 5.8 | Moderate |
| Older or poorly insulated, warm attic | 8.2 | Moderate |
Sealing and insulating a typical attic takes out about 2.0 days a winter here. It drops the risk from moderate to low.
What to do about ice dams in Frederick
- 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.
More on when a roof rake is worth it.
Frederick winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 9.4 | 7.9 | 2.1 |
| February | 11.1 | 8.9 | 2.1 |
| March | 4.8 | 3.3 | 0.5 |
| April | 0.2 | 0.0 | 0.0 |
| November | 0.8 | 0.5 | 0.0 |
| December | 5.1 | 4.9 | 1.0 |
Frederick next to nearby towns
Frederick ranks 4 of 23 Maryland cities here for ice-dam days, behind Hagerstown at 12.1 days.
- Hagerstown, MD 22 mi, 12.1 days
- Gaithersburg, MD 23 mi, 5.8 days
- Waynesboro, PA 24 mi, 12.1 days
- Westminster, MD 24 mi, 7.6 days
- Leesburg, VA 24 mi, 2.8 days
Where these numbers come from
NOAA 1991–2020 climate normals from Damascus 3 SSW, 15.3 miles from Frederick. 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.