Marion County, Missouri · Palmyra
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Marion County averages 37 nights a year at 20°F or colder, mostly November to March, and 39% of its homes predate 1960.
Heavy rain days of an inch or more come about 8.6 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 Marion County spike on heavy-rain days, about 8.6 a year, when sewer mains fill up and water finds the lowest drain.
Roof leaks here come from summer downpours and, with about 80 freeze-thaw days a year, from winter ice dams. Most show up as ceiling stains in the room below.
13% of occupied homes in Marion County heat mainly with wood or propane, below the Missouri county median of 24.5%.
About 59 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
With 12,917 homes and around 28,457 residents, Marion County is 437 square miles of northern Missouri. Palmyra is the county seat; Hannibal and Philadelphia are the next largest communities. Half the homes here were built before 1971, half after.
59/100 Water Damage Risk Index: Elevated Marion County ranks 26 of 114 Missouri counties. See the statewide ranking and method.The three factors where Marion County ranks highest compared with other Missouri counties.
Marion County gets more hard-freeze nights than most of Missouri. In the 2015–2024 record the county logged about 37 nights a year at or below 20°F (27th of 114) and 106 below freezing. Twenty degrees is roughly where uninsulated pipes start to freeze.
Cold snaps are the real risk. The worst in the record lasted 15 days below freezing (ending January 2018), and the low bottomed out near -15°F on January 15, 2024.
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 31 and end around Apr 12.
Marion gets fewer downpours than most Missouri counties, but they still fill basements. The county gets about 38.6 inches of rain and melted snow a year, with 8.6 days of an inch or more (91st of 114). Those downpours cluster in June, July and September, when sump pumps and gutters are tested hardest. The wettest day on record brought 2.81 inches on April 30, 2017. The worst three-day stretch dropped 4.14 inches, ending September 8, 2018, the kind of soaking that overwhelms sump pumps and storm sewers.
The temperature crosses 32°F in both directions on roughly 80 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
63% of homes in Marion County predate 1980, above the Missouri county median of 53%, which ranks 26th of Missouri's 114 counties.
Before 1960 is when 39% 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.
Renters occupy 31% 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
Marion County averages 59 warm, muggy nights a year (lows of 65°F or more) and gets the most rain in July. 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, Marion County homes break down as 55% utility gas, 31% electric, 11% propane and 1% wood. Fires here are likelier to start in the kitchen or the wiring than in the furnace. After any fire, keep the HVAC off until ducts are checked, or soot will travel through the house.
Fire and smoke cleanup: first stepsCoverage
Calls connect to restoration companies that work across Marion County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Lewis and Shelby get more pipe-freeze nights than Marion. Lewis County has the oldest housing nearby, with 67% of homes built before 1980.
By the numbers
| Factor | Marion | Missouri median | Rank |
|---|---|---|---|
| Homes built before 1960 | 39% | 25% | 14 of 114 |
| Homes built before 1980 | 63% | 53% | 26 of 114 |
| Homes built 2000 or later | 15% | 21% | 96 of 114 |
| Manufactured or mobile homes | 4.8% | 9.8% | 98 of 114 |
| Vacant homes | 12% | 15% | 80 of 114 |
| Wood or propane heat | 13% | 25% | 96 of 114 |
| Nights at 20°F or colder | 37/yr | 28/yr | 27 of 114 |
| Days with 1 inch+ of rain | 8.6/yr | 10/yr | 91 of 114 |
| Freeze-thaw days | 80/yr | 77/yr | 40 of 114 |
| Muggy nights (65°F+) | 59/yr | 65/yr | 73 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 Marion County: freezing from November to March, heavy rain in June, July 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