Washington County, Iowa · Washington
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Washington County averages 53 nights a year at 20°F or colder, mostly November to March, and 46% of its homes predate 1960.
Basements flood here mostly in October. Washington County averages 6 days a year with an inch of rain or more.
Sewage backups in Washington County spike on heavy-rain days, about 6 a year, when sewer mains fill up and water finds the lowest drain.
Roof leaks here come from summer downpours and, with about 97 freeze-thaw days a year, from winter ice dams. Most show up as ceiling stains in the room below.
23% of occupied homes in Washington County heat mainly with wood or propane, close to the Iowa county median of 22.1%.
Muggy summer nights, lows of 65°F or more, come about 36 times a year in Washington County. Mold after a leak spreads fastest from June through August.
Local risk profile
Washington County covers 569 square miles of southeast Iowa, with about 22,561 residents and 9,657 homes. The county seat is Washington, and Kalona, Wellman and Riverside round out the largest towns. Half the homes here were built before 1964, half after.
33/100 Water Damage Risk Index: Moderate Washington County ranks 92 of 99 Iowa counties. See the statewide ranking and method.The three factors where Washington County ranks highest compared with other Iowa counties.
Winters here are on the gentler end for Iowa, and pipes still freeze. In the 2015–2024 record the county logged about 53 nights a year at or below 20°F (79th of 99) and 135 below freezing. Twenty degrees is roughly where uninsulated pipes start to freeze.
The longest cold spell was straight 15 days without the temperature rising above freezing, ending in January 2018. The coldest night reached about -28°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 20 and end around Apr 24.
Washington gets fewer downpours than most Iowa counties, but they still fill basements. The county gets about 35.2 inches of rain and melted snow a year, with 6 days of an inch or more (86th of 99). Those downpours cluster in May, June and October, when sump pumps and gutters are tested hardest. The wettest day on record brought 3.78 inches on June 10, 2020. The worst three-day stretch dropped 4.04 inches, ending June 11, 2020, the kind of soaking that overwhelms sump pumps and storm sewers.
Freeze-thaw days, below freezing overnight and above it by afternoon, come about 97 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
66% of homes in Washington County predate 1980, below the Iowa county median of 72.8%, which ranks 71st of Iowa's 99 counties.
Since 2000 the county has added enough housing that 19% of homes are that new. Modern PEX and copper rarely fail on their own; the leaks come from connections, appliances and storms.
Beyond water
Washington County averages 36 warm, muggy nights a year (lows of 65°F or more) and gets the most rain in May. 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 48% utility gas, 27% electric, 20% propane and 3% wood. Wood heat is above the Iowa 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 Washington County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Iowa, Johnson and Keokuk get more pipe-freeze nights than Washington. Keokuk County has the oldest housing nearby, with 80% of homes built before 1980.
By the numbers
| Factor | Washington | Iowa median | Rank |
|---|---|---|---|
| Homes built before 1960 | 46% | 48% | 55 of 99 |
| Homes built before 1980 | 66% | 73% | 71 of 99 |
| Homes built 2000 or later | 19% | 13% | 19 of 99 |
| Manufactured or mobile homes | 3.5% | 3.2% | 41 of 99 |
| Vacant homes | 7.1% | 9.5% | 82 of 99 |
| Wood or propane heat | 23% | 22% | 52 of 99 |
| Nights at 20°F or colder | 53/yr | 62/yr | 79 of 99 |
| Days with 1 inch+ of rain | 6/yr | 7.1/yr | 86 of 99 |
| Freeze-thaw days | 97/yr | 94/yr | 11 of 99 |
| Muggy nights (65°F+) | 36/yr | 29/yr | 27 of 99 |
Rank 1 is the highest value. Bars run from the lowest to the highest Iowa 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, June and October.
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