Polk County, Iowa · Des Moines
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Polk County averages 54 nights a year at 20°F or colder, mostly November to March, and 28% of its homes predate 1960.
Heavy rain days of an inch or more come about 7 times a year here, most often in July. A sump pump that hasn't run since last season is a common weak point.
Backups often follow heavy rain, which Polk County gets about 7 days a year, when storm water overloads sewer mains and pushes up through the lowest drain in the house.
In Polk County, 2.65 inches fell on the wettest day of the 2015–2024 record. Storms like that, and ice dams in snowy winters, cause most roof leaks.
3% of occupied homes in Polk County heat mainly with wood or propane, below the Iowa county median of 22.1%.
With 42 muggy nights a year, mold in Polk County can appear within days of a leak. Dry first, then clean.
Local risk profile
With 218,486 homes and around 503,175 residents, Polk County is 573 square miles of central Iowa. Besides Des Moines, the county seat, the biggest communities are Ankeny, West Des Moines and Urbandale. Half the homes here were built before 1982, half after.
35/100 Water Damage Risk Index: Moderate Polk County ranks 89 of 99 Iowa counties. See the statewide ranking and method.The three factors where Polk County ranks highest compared with other Iowa counties.
Winters here are on the gentler end for Iowa, and pipes still freeze. From 2015–2024 it averaged 54 nights a year at 20°F or colder, the range where pipes in exterior walls, crawl spaces and unheated garages freeze, and 128 nights at or below 32°F. That ranks 71st of 99 counties.
Cold snaps are the real risk. The worst in the record lasted 17 days below freezing (ending February 2021), and the low bottomed out near -23°F on January 31, 2019.
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 23.
Rainfall is about average for Iowa. About 7 days a year bring an inch or more (52nd of 99), most often in July, out of 34.9 inches of total precipitation. On June 25, 2015, 2.65 inches fell in a single day. The worst three-day stretch dropped 3.48 inches, ending September 3, 2018, the kind of soaking that overwhelms sump pumps and storm sewers.
The temperature crosses 32°F in both directions on roughly 87 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
Iowa's 99 counties range widely in housing age; Polk ranks 95th, with 49% of its homes built before 1980.
Growth since 2000 added 31% 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.
Renters occupy 33% 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 42 times a year here, above the Iowa county median of 29. 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 expectBy main heating fuel, Polk County homes break down as 66% utility gas, 31% electric, 2% propane and under 1% 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 Polk County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Boone, Dallas, Jasper and Story get more pipe-freeze nights than Polk. Jasper County has the oldest housing nearby, with 73% of homes built before 1980.
By the numbers
| Factor | Polk | Iowa median | Rank |
|---|---|---|---|
| Homes built before 1960 | 28% | 48% | 93 of 99 |
| Homes built before 1980 | 49% | 73% | 95 of 99 |
| Homes built 2000 or later | 31% | 13% | 5 of 99 |
| Manufactured or mobile homes | 2% | 3.2% | 71 of 99 |
| Vacant homes | 6% | 9.5% | 92 of 99 |
| Wood or propane heat | 2.5% | 22% | 99 of 99 |
| Nights at 20°F or colder | 54/yr | 62/yr | 71 of 99 |
| Days with 1 inch+ of rain | 7/yr | 7.1/yr | 52 of 99 |
| Freeze-thaw days | 87/yr | 94/yr | 95 of 99 |
| Muggy nights (65°F+) | 42/yr | 29/yr | 5 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 Polk County: freezing from November to March, heavy rain in May, June and July.
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