Ice dam risk in Susanville, CA
Ice dams in Susanville, CA: how often
19.8 dam days a winter
High risk. On an ordinary house in Susanville, conditions for an ice dam come on about 19.8 days in a normal winter, mostly in January and February.
Susanville averages 109 inches of snow a year and about 88 days with snow on the ground. Snow that lies that long is what turns a little attic heat into a ridge of ice at the eave. 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 Susanville
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 18.2 | High |
| Typical, some insulation, not air-sealed | 19.8 | High |
| Older or poorly insulated, warm attic | 21.7 | High |
The attic matters less in Susanville than in colder towns: there are only 1.6 days a winter between a typical attic and a sealed one.
What to do about ice dams in Susanville
- 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.
- At the next reroof, ask for ice-and-water membrane under the shingles from the eave to at least 24 inches inside the wall line. It does not stop a dam; it stops the leak when one forms.
- Heat cable is worth pricing here even on a sealed house, along the eave and in the gutters and downspouts it drains into.
Running 60 feet of 5 W/ft cable whenever snow lies below freezing would use about 28 kWh a winter in Susanville, roughly $5 at 17 cents a kWh.
Which to spend on first: air sealing or heat cable.
Susanville winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 28.5 | 21.7 | 5.3 |
| February | 22.3 | 20.4 | 4.8 |
| March | 17.1 | 19.2 | 4.0 |
| April | 7.3 | 4.6 | 0.7 |
| May | 0.5 | 0.1 | 0.0 |
| June | 0.1 | 0.0 | 0.0 |
| October | 0.8 | 0.3 | 0.0 |
| November | 7.1 | 3.8 | 0.7 |
| December | 25.6 | 17.9 | 4.3 |
Susanville next to nearby towns
Susanville ranks 2 of 376 California cities here for ice-dam days, behind Truckee at 36.3 days.
- Reno, NV 74 mi, 3.1 days
- Sparks, NV 77 mi, 1.3 days
- Chico, CA 78 mi, 0.0 days
- Truckee, CA 78 mi, 36.3 days
- Oroville, CA 81 mi, 0.0 days
Where these numbers come from
NOAA 1991–2020 climate normals from Canyon Dam, 30.3 miles from Susanville. 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.
- The weather station is 30 miles away, far enough that local snow can differ.