Ice dam risk in Jefferson City, MO
How often ice dams form in Jefferson City
4.1 dam days a winter
Low risk. On an ordinary house in Jefferson City, conditions for an ice dam come on about 4.1 days in a normal winter, mostly in January and February.
Jefferson City averages 9 inches of snow a year and about 16 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 Jefferson City
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 2.6 | Low |
| Typical, some insulation, not air-sealed | 4.1 | Low |
| Older or poorly insulated, warm attic | 6.0 | Moderate |
The attic matters less in Jefferson City than in colder towns: there are only 1.5 days a winter between a typical attic and a sealed one.
What to do about ice dams in Jefferson City
- Check the gutters before the first snow and clear them, so meltwater has somewhere to go. If you see icicles thicker than a finger along the eave after a storm, that is the early sign to look at the attic.
Snowy places are not always the worst: why snowfall misleads.
Jefferson City winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 2.9 | 7.5 | 2.2 |
| February | 2.9 | 3.7 | 0.9 |
| March | 0.4 | 1.3 | 0.2 |
| November | 0.2 | 0.4 | 0.0 |
| December | 2.5 | 3.1 | 0.8 |
Jefferson City next to nearby towns
Jefferson City ranks 29 of 80 Missouri cities here for ice-dam days, behind Maryville at 9.3 days.
- Fulton, MO 23 mi, 6.3 days
- Columbia, MO 27 mi, 4.6 days
- Mexico, MO 44 mi, 6.3 days
- Rolla, MO 48 mi, 4.1 days
- Sedalia, MO 58 mi, 3.0 days
Where these numbers come from
NOAA 1991–2020 climate normals from Jefferson City Wtp, 1.3 miles from Jefferson City. 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.