Ice dam risk in Mexico, MO
Ice dams in Mexico, MO: how often
6.3 dam days a winter
Moderate risk. On an ordinary house in Mexico, conditions for an ice dam come on about 6.3 days in a normal winter, mostly in January and February.
Mexico averages 19 inches of snow a year and about 23 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 Mexico
| Attic | Dam days | Risk |
|---|---|---|
| Air-sealed and well insulated | 3.8 | Low |
| Typical, some insulation, not air-sealed | 6.3 | Moderate |
| Older or poorly insulated, warm attic | 9.5 | Moderate |
Sealing and insulating a typical attic takes out about 2.5 days a winter here. It drops the risk from moderate to low. An older house with a warm attic should expect closer to 9.5 days.
What to do about ice dams in Mexico
- 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.
Which to spend on first: air sealing or heat cable.
Mexico winter, month by month
| Month | Snow (in) | Days on ground | Dam days |
|---|---|---|---|
| January | 7.2 | 10.3 | 3.3 |
| February | 4.3 | 5.6 | 1.5 |
| March | 1.5 | 1.1 | 0.2 |
| April | 0.3 | 0.0 | 0.0 |
| November | 0.7 | 0.5 | 0.1 |
| December | 4.9 | 5.2 | 1.3 |
Mexico next to nearby towns
Mexico ranks 6 of 80 Missouri cities here for ice-dam days, behind Maryville at 9.3 days.
- Fulton, MO 22 mi, 6.3 days
- Columbia, MO 29 mi, 4.6 days
- Moberly, MO 35 mi, 2.9 days
- Jefferson City, MO 44 mi, 4.1 days
- Hannibal, MO 46 mi, 8.4 days
Where these numbers come from
NOAA 1991–2020 climate normals from Fulton, 22.0 miles from Mexico. 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.