Union County, Iowa · Creston
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Union County averages 56 nights a year at 20°F or colder, mostly November to March, and 48% of its homes predate 1960.
September brings the most downpours to Union County, part of 7.4 heavy-rain days a year. Check the sump first.
48% of homes here predate 1960, when clay and cast iron sewer laterals were standard. Roots and cracks in those lines are a common cause of backups.
In Union County, 2.51 inches fell on the wettest day of the 2015–2024 record. Storms like that, and ice dams in snowy winters, cause most roof leaks.
19% of occupied homes in Union County heat mainly with wood or propane, below the Iowa county median of 22.1%.
With 34 muggy nights a year, mold in Union County can appear within days of a leak. Dry first, then clean.
Local risk profile
With 5,785 homes and around 11,993 residents, Union County is 424 square miles of southern Iowa. The county seat is Creston, and Afton, Lorimor and Shannon City round out the largest towns. The county's median home was built in 1962.
52/100 Water Damage Risk Index: Elevated Union County ranks 42 of 99 Iowa counties. See the statewide ranking and method.The three factors where Union County ranks highest compared with other Iowa counties.
For frozen pipes, Union County is a typical Iowa county, which is still plenty. It averaged 135 freezing nights a year over 2015–2024, 56 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 64th.
On January 1, 2018 the low fell to about -22°F, and in the stretch ending January 2018 the county went 16 days in a row below freezing. Leaks from split pipes typically appear the day the thaw arrives.
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 19 and the last spring freeze around Apr 22.
Rainfall is about average for Iowa. The county gets about 35.5 inches of rain and melted snow a year, with 7.4 days of an inch or more (34th of 99). Those downpours cluster in July, August and September, when sump pumps and gutters are tested hardest. The wettest day on record brought 2.51 inches on July 29, 2015. Multi-day storms matter most for basements; the wettest three days on record here totaled 3.74 inches (through September 3, 2018).
The temperature crosses 32°F in both directions on roughly 98 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 73% of the county's housing was built before 1980. That puts Union near the middle of Iowa's 99 counties.
Housing age is mixed: 48% of homes are pre-1960 and 13% are 2000 or newer. Ask any plumber which era your house is from and you'll know which failures to watch for.
12% of homes were vacant at survey time. A leak in an empty rental or seasonal house can run for days before anyone notices, which is why those losses tend to be larger.
Beyond water
Union County averages 34 warm, muggy nights a year (lows of 65°F or more) and gets the most rain in May. 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 Union County it's 49% utility gas, 31% electric, 17% propane and 1% wood. Most homes here heat with gas or electricity, so cooking and electrical faults are the likelier fire sources. Even a contained kitchen fire can send soot through the ductwork to every room.
Fire and smoke cleanup: first stepsCoverage
Calls connect to restoration companies that work across Union County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Adair and Adams get more pipe-freeze nights than Union. Adair County has the oldest housing nearby, with 77% of homes built before 1980.
By the numbers
| Factor | Union | Iowa median | Rank |
|---|---|---|---|
| Homes built before 1960 | 48% | 48% | 47 of 99 |
| Homes built before 1980 | 73% | 73% | 50 of 99 |
| Homes built 2000 or later | 13% | 13% | 53 of 99 |
| Manufactured or mobile homes | 5.4% | 3.2% | 17 of 99 |
| Vacant homes | 12% | 9.5% | 24 of 99 |
| Wood or propane heat | 19% | 22% | 71 of 99 |
| Nights at 20°F or colder | 56/yr | 62/yr | 64 of 99 |
| Days with 1 inch+ of rain | 7.4/yr | 7.1/yr | 34 of 99 |
| Freeze-thaw days | 98/yr | 94/yr | 3 of 99 |
| Muggy nights (65°F+) | 34/yr | 29/yr | 34 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 Union County: freezing from November to March, heavy rain in July, 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