St. Louis County, Minnesota · Duluth
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With 48% of homes built before 1960 and about 118 hard-freeze nights a year, frozen and split pipes are a leading winter risk in the county.
Heavy rain days of an inch or more come about 3.1 times a year here, most often in September. A sump pump that hasn't run since last season is a common weak point.
Backups often follow heavy rain, which St. Louis County gets about 3.1 days a year, when storm water overloads sewer mains and pushes up through the lowest drain in the house.
In St. Louis County, 3.24 inches fell on the wettest day of the 2015–2024 record. Storms like that, and ice dams in snowy winters, cause most roof leaks.
20% of occupied homes in St. Louis County heat mainly with wood or propane, below the Minnesota county median of 30%.
With 1 muggy night a year, mold in St. Louis County can appear within days of a leak. Dry first, then clean.
Local risk profile
With 104,263 homes and around 200,123 residents, St. Louis County is 6,248 square miles of northeast Minnesota. Duluth is the county seat; Hibbing, Hermantown and Virginia are the next largest communities. Half the homes here were built before 1962, half after.
57/100 Water Damage Risk Index: Elevated St. Louis County ranks 25 of 87 Minnesota counties. See the statewide ranking and method.The three factors where St. Louis County ranks highest compared with other Minnesota counties.
St. Louis County gets more hard-freeze nights than most of Minnesota. From 2015–2024 it averaged 118 nights a year at 20°F or colder, the range where pipes in exterior walls, crawl spaces and unheated garages freeze, and 192 nights at or below 32°F. That ranks 3rd of 87 counties.
The longest cold spell was straight 60 days without the temperature rising above freezing, ending in March 2019. The coldest night reached about -40°F on January 31, 2019. Burst pipes usually show up when a spell like that breaks and the ice thaws.
The freeze season here runs October to April, with January the coldest. If you travel then, leave the thermostat at 55°F or above and open sink cabinets on outside walls.
Freezing nights typically start around Oct 3 and end around May 17.
St. Louis gets fewer downpours than most Minnesota counties, but they still fill basements. The county gets about 29.3 inches of rain and melted snow a year, with 3.1 days of an inch or more (77th of 87). Those downpours cluster in June, August and September, when sump pumps and gutters are tested hardest. The wettest day on record brought 3.24 inches on June 19, 2024. The worst three-day stretch dropped 3.68 inches, ending June 19, 2024, the kind of soaking that overwhelms sump pumps and storm sewers.
About 96 days a year swing from below freezing at night to above freezing by day. Those freeze-thaw cycles feed ice dams on roofs, open cracks in foundations and driveways, and stress pipes that are already marginal.
Housing
Minnesota's 87 counties range widely in housing age; St. Louis ranks 25th, with 70% of its homes built before 1980.
Before 1960 is when 48% of these homes went up. Galvanized supply lines and cast iron drains were standard then, and after 60-plus years both corrode and crack, often out of sight inside a wall or under a slab.
With 16% of homes empty at survey time, landlords and seasonal owners should shut off the main or schedule checks in winter. An unheated vacant house is also where many policies limit freeze coverage.
Renters occupy 29% of homes. If you rent, the building is usually the landlord's to repair, but your belongings are only covered by renters insurance.
Beyond water
Summer nights that don't drop below 65°F, a good marker of humid air, come about once a year here, below the Minnesota county median of 13. 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 expectMain heating fuel in St. Louis County's occupied homes: 51% utility gas, 19% electric, 17% propane and 3% wood. Wood heat is above the Minnesota norm. Annual chimney and vent inspection, which the NFPA recommends, is one of the most effective fire-prevention habits for these homes.
Fire and smoke cleanup: first stepsCoverage
Calls connect to restoration companies that work across St. Louis County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Lake gets more pipe-freeze nights than St. Louis. Its housing is the oldest in the area by share of homes built before 1980.
By the numbers
| Factor | St. Louis | Minnesota median | Rank |
|---|---|---|---|
| Homes built before 1960 | 48% | 34% | 16 of 87 |
| Homes built before 1980 | 70% | 58% | 25 of 87 |
| Homes built 2000 or later | 15% | 21% | 56 of 87 |
| Manufactured or mobile homes | 3.8% | 3.8% | 43 of 87 |
| Vacant homes | 16% | 11% | 25 of 87 |
| Wood or propane heat | 20% | 30% | 63 of 87 |
| Nights at 20°F or colder | 118/yr | 89/yr | 3 of 87 |
| Days with 1 inch+ of rain | 3.1/yr | 5.3/yr | 77 of 87 |
| Freeze-thaw days | 96/yr | 86/yr | 1 of 87 |
| Muggy nights (65°F+) | 1/yr | 13/yr | 84 of 87 |
Rank 1 is the highest value. Bars run from the lowest to the highest Minnesota county; the tick marks the median; orange means higher water damage risk than the median, green means lower.
Questions
Peak risk months in St. Louis County: freezing from October to April, heavy rain in June, August and September.
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