Ice dam risk in St. Joseph, MO
Ice dams in St. Joseph, MO: how often
8.2 dam days a winter
Moderate risk. On an ordinary house in St. Joseph, conditions for an ice dam come on about 8.2 days in a normal winter, mostly in January and February.
St. Joseph averages 21 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 St. Joseph
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 4.9 | Low |
| Typical, some insulation, not air-sealed | 8.2 | Moderate |
| Older or poorly insulated, warm attic | 12.3 | Moderate |
Sealing and insulating a typical attic takes out about 3.3 days a winter here. It drops the risk from moderate to low. An older house with a warm attic should expect closer to 12.3 days.
What to do about ice dams in St. Joseph
- 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.
- 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.
Which to spend on first: air sealing or heat cable.
St. Joseph winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 5.5 | 10.9 | 3.5 |
| February | 5.9 | 7.8 | 2.1 |
| March | 2.2 | 2.7 | 0.4 |
| April | 0.8 | 0.4 | 0.0 |
| May | 0.1 | 0.0 | 0.0 |
| October | 0.3 | 0.2 | 0.0 |
| November | 1.3 | 0.9 | 0.1 |
| December | 5.0 | 7.2 | 2.0 |
St. Joseph next to nearby towns
St. Joseph ranks 3 of 80 Missouri cities here for ice-dam days, behind Maryville at 9.3 days.
- Atchison, KS 22 mi, 5.7 days
- Smithville, MO 28 mi, 5.2 days
- Leavenworth, KS 31 mi, 4.7 days
- Lansing, KS 36 mi, 4.7 days
- Kearney, MO 37 mi, 5.2 days
Where these numbers come from
NOAA 1991–2020 climate normals from Troy 3N, 14.9 miles from St. Joseph. 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.