Ice dam risk in Cheyenne, WY
Ice dams in Cheyenne, WY: how often
10.3 dam days a winter
Moderate risk. On an ordinary house in Cheyenne, conditions for an ice dam come on about 10.3 days in a normal winter, mostly in December and February.
Cheyenne averages 66 inches of snow a year and about 41 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 Cheyenne
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 7.2 | Moderate |
| Typical, some insulation, not air-sealed | 10.3 | Moderate |
| Older or poorly insulated, warm attic | 14.1 | Moderate |
Sealing and insulating a typical attic takes out about 3.1 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 14.1 days.
Preventing ice dams on a Cheyenne 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.
- 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.
Cheyenne winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 5.5 | 6.6 | 1.8 |
| February | 9.4 | 8.0 | 2.4 |
| March | 9.2 | 4.0 | 0.9 |
| April | 11.5 | 3.4 | 0.5 |
| May | 4.0 | 0.9 | 0.0 |
| September | 0.2 | 0.1 | 0.0 |
| October | 6.9 | 2.3 | 0.2 |
| November | 8.0 | 4.3 | 1.0 |
| December | 10.9 | 11.0 | 3.4 |
Cheyenne next to nearby towns
Cheyenne ranks 10 of 11 Wyoming cities here for ice-dam days, behind Jackson at 50.0 days.
- Wellington, CO 32 mi, 11.6 days
- Timnath, CO 42 mi, 11.6 days
- Fort Collins, CO 42 mi, 10.5 days
- Severance, CO 43 mi, 11.6 days
- Laramie, WY 44 mi, 32.6 days
Where these numbers come from
NOAA 1991–2020 climate normals from Cheyenne Wfo, 1.7 miles from Cheyenne. 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.