St. Clair County, Michigan · Port Huron
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Pipes freeze in St. Clair County on about 36 nights a year, mostly December to March. Older homes, 35% of the stock here, are most at risk.
August brings the most downpours to St. Clair County, part of 3.7 heavy-rain days a year. Check the sump first.
Sewage backups in St. Clair County spike on heavy-rain days, about 3.7 a year, when sewer mains fill up and water finds the lowest drain.
St. Clair County's wettest day in the 2015–2024 record brought 2.56 inches, and about 74 freeze-thaw days a year mean ice dams in some winters.
14% of occupied homes in St. Clair County heat mainly with wood or propane, below the Michigan county median of 29%.
With 33 muggy nights a year, mold in St. Clair County can appear within days of a leak. Dry first, then clean.
Local risk profile
About 160,221 people live in St. Clair County, 722 square miles in southeast Michigan, in roughly 72,799 homes. The county seat is Port Huron, and Marysville, St. Clair and Pearl Beach round out the largest towns. The county's median home was built in 1975.
46/100 Water Damage Risk Index: Elevated St. Clair County ranks 53 of 83 Michigan counties. See the statewide ranking and method.The three factors where St. Clair County ranks highest compared with other Michigan counties.
St. Clair County is milder than most of Michigan, but not mild enough to skip winterizing. In the 2015–2024 record the county logged about 36 nights a year at or below 20°F (78th of 83) and 111 below freezing. Twenty degrees is roughly where uninsulated pipes start to freeze.
Cold snaps are the real risk. The worst in the record lasted 22 days below freezing (ending March 2015), and the low bottomed out near -17°F on February 20, 2015.
Most freezing nights fall from December to March, peaking in January. Disconnect garden hoses and shut off outdoor spigots before the first hard frost, and keep the heat at 55°F or higher if you'll be away.
On average the first fall freeze arrives around Nov 7 and the last spring freeze around Apr 26.
Rainfall is about average for Michigan. Of roughly 34 inches of yearly precipitation, the damage comes from the 3.7 days a year with an inch or more, ranked 46th of 83. March, June and August see the most. The single wettest day in the record: 2.56 inches, June 26, 2021. Multi-day storms matter most for basements; the wettest three days on record here totaled 4.27 inches (through September 24, 2021).
Freeze-thaw days, below freezing overnight and above it by afternoon, come about 74 times a year here. They're the main driver of ice dams and of water working its way through foundation cracks in late winter.
Housing
Michigan's 83 counties range widely in housing age; St. Clair ranks 48th, with 57% of its homes built before 1980.
The mix runs from 35% built before 1960 to 17% built since 2000, so older neighborhoods bring aging pipe while newer subdivisions bring failed appliance lines and water heaters.
The 1980s and 1990s account for 26% of the county's homes. If yours is from those decades, look under the sinks and at the water heater for gray plastic pipe stamped PB, which is polybutylene and leak-prone.
Beyond water
About 33 nights a year in St. Clair County stay at 65°F or warmer, a sign of muggy summer air (4th of 83 counties). August is the wettest month. Keep indoor humidity under 60%, as the EPA advises, and dry any leak within 24 to 48 hours; in a humid month a wet basement left alone won't dry by itself.
Mold remediation: what to expectHeating fuel matters for fire risk. In St. Clair County it's 74% utility gas, 9% electric, 12% propane and 3% wood. Heating equipment, cooking and electrical failures cause most home fires nationally. Even a small kitchen fire can leave soot through the whole house, because smoke follows air currents into closets, ducts and attic space.
Fire and smoke cleanup: first stepsCoverage
Calls connect to restoration companies that work across St. Clair County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Lapeer and Sanilac get more pipe-freeze nights than St. Clair. Sanilac County has the oldest housing nearby, with 63% of homes built before 1980.
By the numbers
| Factor | St. Clair | Michigan median | Rank |
|---|---|---|---|
| Homes built before 1960 | 35% | 32% | 30 of 83 |
| Homes built before 1980 | 57% | 58% | 48 of 83 |
| Homes built 2000 or later | 17% | 16% | 40 of 83 |
| Manufactured or mobile homes | 6.5% | 7.3% | 50 of 83 |
| Vacant homes | 6.8% | 20% | 70 of 83 |
| Wood or propane heat | 14% | 29% | 66 of 83 |
| Nights at 20°F or colder | 36/yr | 54/yr | 78 of 83 |
| Days with 1 inch+ of rain | 3.7/yr | 3.9/yr | 46 of 83 |
| Freeze-thaw days | 74/yr | 95/yr | 83 of 83 |
| Muggy nights (65°F+) | 33/yr | 10/yr | 4 of 83 |
Rank 1 is the highest value. Bars run from the lowest to the highest Michigan county; the tick marks the median; orange means higher water damage risk than the median, green means lower.
Questions
Peak risk months in St. Clair County: freezing from December to March, heavy rain in March, June and August.
Sources: U.S. Census Bureau, ACS 2024 5-year estimates (2020-2024); weather from NOAA nClimGrid-Daily county averages (EpiNOAA), 2015–2024, averaged across the county; county boundaries from Census TIGER. Reviewed 2026-10-21. Methodology