Ice dam risk in Maryville, MO
Ice dams in Maryville, MO: how often
9.3 dam days a winter
Moderate risk. On an ordinary house in Maryville, conditions for an ice dam come on about 9.3 days in a normal winter, mostly in January and February.
Maryville averages 15 inches of snow a year and about 30 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 Maryville
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 5.3 | Moderate |
| Typical, some insulation, not air-sealed | 9.3 | Moderate |
| Older or poorly insulated, warm attic | 14.3 | Moderate |
Sealing and insulating a typical attic takes out about 4.0 days a winter here. It does not move the risk band, but it shortens every dam. An older house with a warm attic should expect closer to 14.3 days.
Preventing ice dams on a Maryville roof
- Air-seal the attic floor: the gaps around the hatch, light fixtures, plumbing stacks and the top plates of interior walls. This is the fix that removes the cause, and it usually costs less than a season of contractor ice removal.
Which to spend on first: air sealing or heat cable.
Maryville winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 5.2 | 11.1 | 3.9 |
| February | 4.4 | 8.3 | 2.6 |
| March | 1.6 | 2.3 | 0.4 |
| April | 0.8 | 0.4 | 0.0 |
| October | 0.1 | 0.0 | 0.0 |
| November | 0.6 | 1.4 | 0.3 |
| December | 2.6 | 6.7 | 2.1 |
Maryville next to nearby towns
Maryville ranks 1 of 80 Missouri cities here for ice-dam days, the worst in the state.
- St. Joseph, MO 40 mi, 8.2 days
- Atchison, KS 56 mi, 5.7 days
- Smithville, MO 67 mi, 5.2 days
- Leavenworth, KS 71 mi, 4.7 days
- Kearney, MO 73 mi, 5.2 days
Where these numbers come from
NOAA 1991–2020 climate normals from Maryville 2E, 1.9 miles from Maryville. 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.