Ice dam risk in Washington, MO
Will your roof get ice dams in Washington, MO?
3.7 dam days a winter
Low risk. On an ordinary house in Washington, conditions for an ice dam come on about 3.7 days in a normal winter, mostly in January and December.
Washington averages 8 inches of snow a year and about 14 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 Washington
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 2.5 | Low |
| Typical, some insulation, not air-sealed | 3.7 | Low |
| Older or poorly insulated, warm attic | 5.2 | Moderate |
The attic matters less in Washington than in colder towns: there are only 1.2 days a winter between a typical attic and a sealed one.
What to do about ice dams in Washington
- 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.
Washington winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 2.6 | 6.2 | 1.8 |
| February | 1.4 | 2.8 | 0.7 |
| March | 0.7 | 0.9 | 0.1 |
| April | 0.1 | 0.1 | 0.0 |
| November | 0.4 | 0.5 | 0.1 |
| December | 2.7 | 3.9 | 0.9 |
Washington next to nearby towns
Washington ranks 38 of 80 Missouri cities here for ice-dam days, behind Maryville at 9.3 days.
- Union, MO 8 mi, 3.1 days
- Wildwood, MO 19 mi, 3.6 days
- Wentzville, MO 20 mi, 3.6 days
- Lake St. Louis, MO 20 mi, 3.6 days
- Eureka, MO 20 mi, 3.6 days
Where these numbers come from
NOAA 1991–2020 climate normals from Washington, 2.3 miles from Washington. 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.