Washington County, Minnesota · Stillwater
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Washington County averages 76 nights a year at 20°F or colder, mostly November to March, and 13% of its homes predate 1960.
Basements flood here mostly in August. Washington County averages 5.6 days a year with an inch of rain or more.
Sewage backups in Washington County spike on heavy-rain days, about 5.6 a year, when sewer mains fill up and water finds the lowest drain.
Roof leaks here come from summer downpours and, with about 81 freeze-thaw days a year, from winter ice dams. Most show up as ceiling stains in the room below.
3% of occupied homes in Washington County heat mainly with wood or propane, below the Minnesota county median of 30%.
Muggy summer nights, lows of 65°F or more, come about 23 times a year in Washington County. Mold after a leak spreads fastest from June through August.
Local risk profile
Washington County covers 385 square miles of southern Minnesota, with about 276,238 residents and 109,307 homes. The county seat is Stillwater, and Woodbury, Cottage Grove and Oakdale round out the largest towns. Much of its housing is recent, with a median build year of 1992.
33/100 Water Damage Risk Index: Moderate Washington County ranks 82 of 87 Minnesota counties. See the statewide ranking and method.The three factors where Washington County ranks highest compared with other Minnesota counties.
Winters here are on the gentler end for Minnesota, and pipes still freeze. In the 2015–2024 record the county logged about 76 nights a year at or below 20°F (81st of 87) and 149 below freezing. Twenty degrees is roughly where uninsulated pipes start to freeze.
The longest cold spell was straight 32 days without the temperature rising above freezing, ending in March 2019. The coldest night reached about -31°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 November to March, 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 22 and end around May 1.
Rainfall is about average for Minnesota. The county gets about 32.8 inches of rain and melted snow a year, with 5.6 days of an inch or more (34th of 87). Those downpours cluster in May, July and August, when sump pumps and gutters are tested hardest. The wettest day on record brought 3.4 inches on August 11, 2016. The worst three-day stretch dropped 3.73 inches, ending August 13, 2016, the kind of soaking that overwhelms sump pumps and storm sewers.
Freeze-thaw days, below freezing overnight and above it by afternoon, come about 81 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
33% of homes in Washington County predate 1980, below the Minnesota county median of 58.4%, which ranks 83rd of Minnesota's 87 counties.
Since 2000 the county has added enough housing that 34% of homes are that new. Modern PEX and copper rarely fail on their own; the leaks come from connections, appliances and storms.
34% date from 1980 to 1999, the window when polybutylene, a gray flexible plastic supply pipe, was used in some homes. It's prone to leaks at the fittings, so it's worth checking for in a house from those years.
Beyond water
Washington County averages 23 warm, muggy nights a year (lows of 65°F or more) and gets the most rain in August. The EPA recommends keeping indoor humidity below 60%, ideally 30 to 50%. Basements can pass 60% on their own in summer, so a dehumidifier matters even without a leak, and anything wet should be dried within 24 to 48 hours.
Mold remediation: what to expectBy main heating fuel, Washington County homes break down as 80% utility gas, 16% electric, 2% propane and under 1% wood. Most homes here heat with gas or electricity, so cooking and electrical faults are the likelier fire sources. Even a contained kitchen fire can send soot through the ductwork to every room.
Fire and smoke cleanup: first stepsCoverage
Calls connect to restoration companies that work across Washington County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Anoka and Chisago get more pipe-freeze nights than Washington. Ramsey County has the oldest housing nearby, with 69% of homes built before 1980.
By the numbers
| Factor | Washington | Minnesota median | Rank |
|---|---|---|---|
| Homes built before 1960 | 13% | 34% | 82 of 87 |
| Homes built before 1980 | 33% | 58% | 83 of 87 |
| Homes built 2000 or later | 34% | 21% | 6 of 87 |
| Manufactured or mobile homes | 1.8% | 3.8% | 72 of 87 |
| Vacant homes | 3.4% | 11% | 83 of 87 |
| Wood or propane heat | 2.7% | 30% | 84 of 87 |
| Nights at 20°F or colder | 76/yr | 89/yr | 81 of 87 |
| Days with 1 inch+ of rain | 5.6/yr | 5.3/yr | 34 of 87 |
| Freeze-thaw days | 81/yr | 86/yr | 80 of 87 |
| Muggy nights (65°F+) | 23/yr | 13/yr | 3 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 Washington County: freezing from November to March, heavy rain in May, July 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