Ice dam risk in Pella, IA
Ice dams in Pella, IA: how often
14.7 dam days a winter
Moderate risk. On an ordinary house in Pella, conditions for an ice dam come on about 14.7 days in a normal winter, mostly in January and February.
Pella averages 29 inches of snow a year and about 44 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 Pella
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 6.9 | Moderate |
| Typical, some insulation, not air-sealed | 14.7 | Moderate |
| Older or poorly insulated, warm attic | 24.5 | High |
Sealing and insulating a typical attic takes out about 7.8 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 24.5 days.
What to do about ice dams in Pella
- 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.
Pella winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 9.2 | 16.2 | 6.4 |
| February | 6.0 | 12.4 | 4.3 |
| March | 4.5 | 4.4 | 0.9 |
| April | 0.8 | 0.4 | 0.0 |
| October | 0.3 | 0.1 | 0.0 |
| November | 1.6 | 1.8 | 0.4 |
| December | 6.3 | 8.2 | 2.8 |
Pella next to nearby towns
Pella ranks 35 of 41 Iowa cities here for ice-dam days, behind Mason City at 28.7 days.
- Oskaloosa, IA 16 mi, 11.9 days
- Newton, IA 21 mi, 19.6 days
- Pleasant Hill, IA 33 mi, 16.1 days
- Altoona, IA 34 mi, 17.4 days
- Indianola, IA 34 mi, 16.6 days
Where these numbers come from
NOAA 1991–2020 climate normals from Newton, 22.0 miles from Pella. 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.