Ice dam risk in Riverton, WY
Ice dams in Riverton, WY: how often
25.7 dam days a winter
High risk. On an ordinary house in Riverton, conditions for an ice dam come on about 25.7 days in a normal winter, mostly in January and December.
Riverton averages 44 inches of snow a year and about 76 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 Riverton
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 13.5 | Moderate |
| Typical, some insulation, not air-sealed | 25.7 | High |
| Older or poorly insulated, warm attic | 40.9 | Severe |
Sealing and insulating a typical attic takes out about 12.2 days a winter here. It drops the risk from high to moderate. An older house with a warm attic should expect closer to 40.9 days.
What to do about ice dams in Riverton
- 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.
- 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.
Which to spend on first: air sealing or heat cable.
Riverton winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 5.5 | 22.7 | 8.9 |
| February | 7.4 | 16.5 | 5.5 |
| March | 6.5 | 6.4 | 1.6 |
| April | 7.2 | 2.5 | 0.4 |
| May | 2.1 | 0.5 | 0.0 |
| September | 0.6 | 0.2 | 0.0 |
| October | 4.4 | 2.0 | 0.3 |
| November | 5.3 | 7.2 | 2.1 |
| December | 5.3 | 17.7 | 6.9 |
Riverton next to nearby towns
Riverton ranks 4 of 11 Wyoming cities here for ice-dam days, behind Jackson at 50.0 days.
- Casper, WY 105 mi, 18.5 days
- Rock Springs, WY 108 mi, 13.9 days
- Cody, WY 109 mi, 7.3 days
- Green River, WY 118 mi, 23.1 days
- Jackson, WY 124 mi, 50.0 days
Where these numbers come from
NOAA 1991–2020 climate normals from Riverton, 0.5 miles from Riverton. 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.