Winneshiek County, Iowa · Decorah
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Pipes freeze in Winneshiek County on about 70 nights a year, mostly November to April. Older homes, 49% of the stock here, are most at risk.
July brings the most downpours to Winneshiek County, part of 9.2 heavy-rain days a year. Check the sump first.
Sewage backups in Winneshiek County spike on heavy-rain days, about 9.2 a year, when sewer mains fill up and water finds the lowest drain.
Winneshiek County's wettest day in the 2015–2024 record brought 3.78 inches, and about 93 freeze-thaw days a year mean ice dams in some winters.
40% of occupied homes in Winneshiek County heat mainly with wood or propane, above the Iowa county median of 22.1%.
About 17 nights a year here stay at 65°F or warmer, so basements and crawl spaces can grow mold even without a leak.
Local risk profile
About 19,873 people live in Winneshiek County, 690 square miles in northeast Iowa, in roughly 9,029 homes. The county seat is Decorah, and Calmar, Ossian and Spillville round out the largest towns. The county's median home was built in 1962.
65/100 Water Damage Risk Index: Elevated Winneshiek County ranks 15 of 99 Iowa counties. See the statewide ranking and method.The three factors where Winneshiek County ranks highest compared with other Iowa counties.
Winneshiek is on the colder side of Iowa for pipes. It averaged 153 freezing nights a year over 2015–2024, 70 of them at 20°F or colder, cold enough for pipes in outside walls and crawl spaces to freeze. Among 99 Iowa counties that's 25th.
The longest cold spell was straight 21 days without the temperature rising above freezing, ending in March 2019. The coldest night reached about -33°F on January 31, 2019. Burst pipes usually show up when a spell like that breaks and the ice thaws.
Most freezing nights fall from November to April, 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 Oct 14 and the last spring freeze around May 4.
Heavy rain is a bigger factor here than in most of Iowa. About 9.2 days a year bring an inch or more (2nd of 99), most often in July, out of 40.1 inches of total precipitation. On August 24, 2016, 3.78 inches fell in a single day. Multi-day storms matter most for basements; the wettest three days on record here totaled 4.28 inches (through September 23, 2016).
The temperature crosses 32°F in both directions on roughly 93 days a year. Each cycle melts and refreezes water at roof edges and in foundation cracks, which is how ice dams and basement seepage get started.
Housing
Roughly 67% of the county's housing was built before 1980. That puts Winneshiek near the middle of Iowa's 99 counties.
Growth since 2000 added 18% of today's homes. In houses that new, the weak points are washing machine hoses, ice maker lines, water heaters and sump pumps rather than the pipes in the walls.
Beyond water
Winneshiek County averages 17 warm, muggy nights a year (lows of 65°F or more) and gets the most rain in June. Mold grows when indoor humidity stays above about 60%, the EPA's ceiling. A basement dehumidifier set to 50% and drying anything wet within 24 to 48 hours prevents most problems.
Mold remediation: what to expectMain heating fuel in Winneshiek County's occupied homes: 42% utility gas, 15% electric, 36% propane and 3% wood. Wood and propane heat are 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 Winneshiek County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Chickasaw, Fayette and Howard get more pipe-freeze nights than Winneshiek. Howard County has the oldest housing nearby, with 77% of homes built before 1980.
By the numbers
| Factor | Winneshiek | Iowa median | Rank |
|---|---|---|---|
| Homes built before 1960 | 49% | 48% | 46 of 99 |
| Homes built before 1980 | 67% | 73% | 66 of 99 |
| Homes built 2000 or later | 18% | 13% | 25 of 99 |
| Manufactured or mobile homes | 1.7% | 3.2% | 79 of 99 |
| Vacant homes | 9.9% | 9.5% | 42 of 99 |
| Wood or propane heat | 40% | 22% | 7 of 99 |
| Nights at 20°F or colder | 70/yr | 62/yr | 25 of 99 |
| Days with 1 inch+ of rain | 9.2/yr | 7.1/yr | 2 of 99 |
| Freeze-thaw days | 93/yr | 94/yr | 54 of 99 |
| Muggy nights (65°F+) | 17/yr | 29/yr | 92 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 Winneshiek County: freezing from November to April, heavy rain in June, July 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