O'Brien County, Iowa · Primghar
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O'Brien County averages 78 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 6.9 times a year here, most often in June. A sump pump that hasn't run since last season is a common weak point.
Sewage backups in O'Brien County spike on heavy-rain days, about 6.9 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.
11% of occupied homes in O'Brien County heat mainly with wood or propane, below the Iowa county median of 22.1%.
About 22 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 14,126 people live in O'Brien County, 573 square miles in northwest Iowa, in roughly 6,564 homes. Besides Primghar, the county seat, the biggest communities are Sheldon, Hartley and Sanborn. It has some of the oldest housing in the state: the median home went up in 1959.
63/100 Water Damage Risk Index: Elevated O'Brien County ranks 17 of 99 Iowa counties. See the statewide ranking and method.The three factors where O'Brien County ranks highest compared with other Iowa counties.
O'Brien County gets more hard-freeze nights than most of Iowa. From 2015–2024 it averaged 78 nights a year at 20°F or colder, the range where pipes in exterior walls, crawl spaces and unheated garages freeze, and 156 nights at or below 32°F. That ranks 5th of 99 counties.
On February 16, 2021 the low fell to about -26°F, and in the stretch ending March 2019 the county went 33 days in a row below freezing. Leaks from split pipes typically appear the day the thaw arrives.
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 11 and end around Apr 26.
Rainfall is about average for Iowa. The county gets about 33.2 inches of rain and melted snow a year, with 6.9 days of an inch or more (58th of 99). Those downpours cluster in June, August and September, when sump pumps and gutters are tested hardest. The wettest day on record brought 3.6 inches on June 21, 2018. The worst three-day stretch dropped 6.62 inches, ending September 21, 2018, 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
Roughly 74% of the county's housing was built before 1980. That puts O'Brien near the middle of Iowa's 99 counties.
Before 1960 is when 52% of these homes went up. Galvanized supply lines and cast iron drains were standard then, and after 60-plus years both corrode and crack, often out of sight inside a wall or under a slab.
The Census counted 12% of homes as vacant, above the Iowa county median of 9.5%. Empty houses are where a small leak turns into a large claim, because nobody is there to hear it.
Beyond water
O'Brien County averages 22 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 expectHeating fuel matters for fire risk. In O'Brien County it's 55% utility gas, 32% electric, 11% 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 O'Brien County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Osceola gets more pipe-freeze nights than O'Brien. It also has the most heavy-rain days in its area. Cherokee County has the oldest housing nearby, with 84% of homes built before 1980.
By the numbers
| Factor | O'Brien | Iowa median | Rank |
|---|---|---|---|
| Homes built before 1960 | 52% | 48% | 32 of 99 |
| Homes built before 1980 | 74% | 73% | 45 of 99 |
| Homes built 2000 or later | 11% | 13% | 66 of 99 |
| Manufactured or mobile homes | 2.4% | 3.2% | 64 of 99 |
| Vacant homes | 12% | 9.5% | 25 of 99 |
| Wood or propane heat | 11% | 22% | 88 of 99 |
| Nights at 20°F or colder | 78/yr | 62/yr | 5 of 99 |
| Days with 1 inch+ of rain | 6.9/yr | 7.1/yr | 58 of 99 |
| Freeze-thaw days | 97/yr | 94/yr | 11 of 99 |
| Muggy nights (65°F+) | 22/yr | 29/yr | 71 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 O'Brien 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