Cass County, Iowa · Atlantic
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With 55% of homes built before 1960 and about 58 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 7.2 times a year here, most often in August. A sump pump that hasn't run since last season is a common weak point.
Backups often follow heavy rain, which Cass County gets about 7.2 days a year, when storm water overloads sewer mains and pushes up through the lowest drain in the house.
In Cass County, 4.1 inches fell on the wettest day of the 2015–2024 record. Storms like that, and ice dams in snowy winters, cause most roof leaks.
16% of occupied homes in Cass County heat mainly with wood or propane, below the Iowa county median of 22.1%.
Muggy summer nights, lows of 65°F or more, come about 30 times a year in Cass County. Mold after a leak spreads fastest from June through August.
Local risk profile
Cass County covers 564 square miles of southwest Iowa, with about 13,096 residents and 6,393 homes. The county seat is Atlantic, and Griswold, Anita and Lewis round out the largest towns. It has some of the oldest housing in the state: the median home went up in 1956.
59/100 Water Damage Risk Index: Elevated Cass County ranks 24 of 99 Iowa counties. See the statewide ranking and method.The three factors where Cass County ranks highest compared with other Iowa counties.
Pipe-freeze risk in Cass County sits near the middle of the state. From 2015–2024 it averaged 58 nights a year at 20°F or colder, the range where pipes in exterior walls, crawl spaces and unheated garages freeze, and 136 nights at or below 32°F. That ranks 57th of 99 counties.
Cold snaps are the real risk. The worst in the record lasted 16 days below freezing (ending January 2018), and the low bottomed out near -24°F on February 16, 2021.
Expect the hardest freezes in January, inside a season that runs November to March. That's when an outdoor spigot left connected to a hose, or a pipe in a crawl space, is most likely to split.
Freezing nights typically start around Oct 19 and end around Apr 24.
Rainfall is about average for Iowa. Of roughly 34.3 inches of yearly precipitation, the damage comes from the 7.2 days a year with an inch or more, ranked 42nd of 99. May, August and September see the most. The single wettest day in the record: 4.1 inches, August 20, 2018. The worst three-day stretch dropped 4.93 inches, ending August 22, 2018, the kind of soaking that overwhelms sump pumps and storm sewers.
The temperature crosses 32°F in both directions on roughly 97 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; Cass ranks 20th, with 79% of its homes built before 1980.
55% were built before 1960. Homes from that era often still have galvanized steel supply pipe, which rusts from the inside until it pinholes, and cast iron drains that crack with age. Slow leaks behind walls are a common start to water damage in these houses.
Beyond water
Summer nights that don't drop below 65°F, a good marker of humid air, come about 30 times a year here, close to the Iowa county median of 29. 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 expectHeating fuel matters for fire risk. In Cass County it's 57% utility gas, 27% electric, 15% 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 Cass County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Adair, Audubon and Shelby get more pipe-freeze nights than Cass. Audubon County has the oldest housing nearby, with 84% of homes built before 1980.
By the numbers
| Factor | Cass | Iowa median | Rank |
|---|---|---|---|
| Homes built before 1960 | 55% | 48% | 17 of 99 |
| Homes built before 1980 | 79% | 73% | 20 of 99 |
| Homes built 2000 or later | 8.7% | 13% | 88 of 99 |
| Manufactured or mobile homes | 2.3% | 3.2% | 67 of 99 |
| Vacant homes | 8.6% | 9.5% | 61 of 99 |
| Wood or propane heat | 16% | 22% | 76 of 99 |
| Nights at 20°F or colder | 58/yr | 62/yr | 57 of 99 |
| Days with 1 inch+ of rain | 7.2/yr | 7.1/yr | 42 of 99 |
| Freeze-thaw days | 97/yr | 94/yr | 11 of 99 |
| Muggy nights (65°F+) | 30/yr | 29/yr | 45 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 Cass County: freezing from November to March, heavy rain in May, 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