Cerro Gordo County, Iowa · Mason City
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Cerro Gordo County averages 73 nights a year at 20°F or colder, mostly November to March, and 52% of its homes predate 1960.
Heavy rain days of an inch or more come about 7.2 times a year here, most often in June. A sump pump that hasn't run since last season is a common weak point.
Backups often follow heavy rain, which Cerro Gordo County gets about 7.2 days a year, when storm water overloads sewer mains and pushes up through the lowest drain in the house.
Roof leaks here come from summer downpours and, with about 93 freeze-thaw days a year, from winter ice dams. Most show up as ceiling stains in the room below.
10% of occupied homes in Cerro Gordo County heat mainly with wood or propane, below the Iowa county median of 22.1%.
About 18 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 42,632 people live in Cerro Gordo County, 568 square miles in northern Iowa, in roughly 22,786 homes. The county seat is Mason City, and Clear Lake, Rockwell and Ventura round out the largest towns. It has some of the oldest housing in the state: the median home went up in 1959.
62/100 Water Damage Risk Index: Elevated Cerro Gordo County ranks 18 of 99 Iowa counties. See the statewide ranking and method.The three factors where Cerro Gordo County ranks highest compared with other Iowa counties.
Cerro Gordo is on the colder side of Iowa for pipes. From 2015–2024 it averaged 73 nights a year at 20°F or colder, the range where pipes in exterior walls, crawl spaces and unheated garages freeze, and 151 nights at or below 32°F. That ranks 17th of 99 counties.
The longest cold spell was straight 19 days without the temperature rising above freezing, ending in February 2019. 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.
Most freezing nights fall from November to March, 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 13 and the last spring freeze around May 1.
Rainfall is about average for Iowa. About 7.2 days a year bring an inch or more (42nd of 99), most often in June, out of 36.4 inches of total precipitation. On September 22, 2016, 3.18 inches fell in a single day. Multi-day storms matter most for basements; the wettest three days on record here totaled 4.86 inches (through September 21, 2018).
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
74% of homes in Cerro Gordo County predate 1980, close to the Iowa county median of 72.8%, which ranks 42nd of Iowa's 99 counties.
52% 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.
With 14% of homes empty at survey time, landlords and seasonal owners should shut off the main or schedule checks in winter. An unheated vacant house is also where many policies limit freeze coverage.
Renters occupy 30% 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 18 times a year here, below the Iowa county median of 29. 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, Cerro Gordo County homes break down as 71% utility gas, 18% electric, 10% 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 Cerro Gordo County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Hancock, Mitchell and Worth get more pipe-freeze nights than Cerro Gordo. Franklin County has the oldest housing nearby, with 85% of homes built before 1980.
By the numbers
| Factor | Cerro Gordo | Iowa median | Rank |
|---|---|---|---|
| Homes built before 1960 | 52% | 48% | 29 of 99 |
| Homes built before 1980 | 74% | 73% | 42 of 99 |
| Homes built 2000 or later | 12% | 13% | 60 of 99 |
| Manufactured or mobile homes | 3.2% | 3.2% | 47 of 99 |
| Vacant homes | 14% | 9.5% | 17 of 99 |
| Wood or propane heat | 9.9% | 22% | 90 of 99 |
| Nights at 20°F or colder | 73/yr | 62/yr | 17 of 99 |
| Days with 1 inch+ of rain | 7.2/yr | 7.1/yr | 42 of 99 |
| Freeze-thaw days | 93/yr | 94/yr | 54 of 99 |
| Muggy nights (65°F+) | 18/yr | 29/yr | 89 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 Cerro Gordo County: freezing from November to March, heavy rain in June, 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