Oregon County, Missouri · Alton
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Oregon County averages 18 nights a year at 20°F or colder, mostly December to February, and 26% of its homes predate 1960.
May brings the most downpours to Oregon County, part of 13.2 heavy-rain days a year. Check the sump first.
Backups often follow heavy rain, which Oregon County gets about 13.2 days a year, when storm water overloads sewer mains and pushes up through the lowest drain in the house.
In Oregon County, 3.97 inches fell on the wettest day of the 2015–2024 record. Storms like that, and ice dams in snowy winters, cause most roof leaks.
54% of occupied homes in Oregon County heat mainly with wood or propane, above the Missouri county median of 24.5%.
Muggy summer nights, lows of 65°F or more, come about 71 times a year in Oregon County. Mold after a leak spreads fastest from June through August.
Local risk profile
About 8,673 people live in Oregon County, 790 square miles in southern Missouri, in roughly 4,321 homes. The county seat is Alton, and Thayer, Koshkonong and Thomasville round out the largest towns. Half the homes here were built before 1978, half after.
53/100 Water Damage Risk Index: Elevated Oregon County ranks 50 of 114 Missouri counties. See the statewide ranking and method.The three factors where Oregon County ranks highest compared with other Missouri counties.
Winters here are on the gentler end for Missouri, and pipes still freeze. From 2015–2024 it averaged 18 nights a year at 20°F or colder, the range where pipes in exterior walls, crawl spaces and unheated garages freeze, and 81 nights at or below 32°F. That ranks 103rd of 114 counties.
The longest cold spell was straight 10 days without the temperature rising above freezing, ending in February 2021. The coldest night reached about -5°F on February 16, 2021. Burst pipes usually show up when a spell like that breaks and the ice thaws.
Most freezing nights fall from December to February, 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.
Freezing nights typically start around Oct 29 and end around Mar 29.
Heavy rain is a bigger factor here than in most of Missouri. The county gets about 51.4 inches of rain and melted snow a year, with 13.2 days of an inch or more (9th of 114). Those downpours cluster in March, May and August, when sump pumps and gutters are tested hardest. The wettest day on record brought 3.97 inches on April 30, 2017. The worst three-day stretch dropped 6.71 inches, ending November 6, 2024, the kind of soaking that overwhelms sump pumps and storm sewers.
Freeze-thaw days, below freezing overnight and above it by afternoon, come about 74 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
54% of homes in Oregon County predate 1980, close to the Missouri county median of 53%, which ranks 54th of Missouri's 114 counties.
Older and newer homes sit side by side here: 26% predate 1960 and 20% are from 2000 or later. Corroded pipe is the typical failure in the first group, burst supply hoses in the second.
The 1980s and 1990s account for 26% of the county's homes. If yours is from those decades, look under the sinks and at the water heater for gray plastic pipe stamped PB, which is polybutylene and leak-prone.
17% of homes are manufactured or mobile homes, above the Missouri county median of 9.8%. Their water lines run under the floor behind the skirting, so a torn skirt or failed heat tape freezes them faster than lines in a site-built house.
The Census counted 22% of homes as vacant, above the Missouri county median of 15.3%. Empty houses are where a small leak turns into a large claim, because nobody is there to hear it.
Beyond water
Oregon County averages 71 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 Oregon County it's 2% utility gas, 41% electric, 41% propane and 14% wood. Wood and propane heat are more common here than the state median. Have chimneys swept and fuel-burning appliances serviced each fall, and keep three feet clear around stoves and space heaters.
Fire and smoke cleanup: first stepsCoverage
Calls connect to restoration companies that work across Oregon County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Carter, Howell and Shannon get more pipe-freeze nights than Oregon. Its housing is the oldest in the area by share of homes built before 1980.
By the numbers
| Factor | Oregon | Missouri median | Rank |
|---|---|---|---|
| Homes built before 1960 | 26% | 25% | 55 of 114 |
| Homes built before 1980 | 54% | 53% | 54 of 114 |
| Homes built 2000 or later | 20% | 21% | 62 of 114 |
| Manufactured or mobile homes | 17% | 9.8% | 13 of 114 |
| Vacant homes | 22% | 15% | 27 of 114 |
| Wood or propane heat | 54% | 25% | 4 of 114 |
| Nights at 20°F or colder | 18/yr | 28/yr | 103 of 114 |
| Days with 1 inch+ of rain | 13/yr | 10/yr | 9 of 114 |
| Freeze-thaw days | 74/yr | 77/yr | 77 of 114 |
| Muggy nights (65°F+) | 71/yr | 65/yr | 27 of 114 |
Rank 1 is the highest value. Bars run from the lowest to the highest Missouri county; the tick marks the median; orange means higher water damage risk than the median, green means lower.
Questions
Peak risk months in Oregon County: freezing from December to February, heavy rain in March, May and August.
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