Union County, South Carolina · Union
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Union County averages 3 nights a year at 20°F or colder, mostly December to January, and 31% of its homes predate 1960.
December brings the most downpours to Union County, part of 10.6 heavy-rain days a year. Check the sump first.
31% 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, 5.39 inches fell on the wettest day of the 2015–2024 record. Storms like that, and ice dams in snowy winters, cause most roof leaks.
9% of occupied homes in Union County heat mainly with wood or propane, above the South Carolina county median of 5.1%.
With 96 muggy nights a year, mold in Union County can appear within days of a leak. Dry first, then clean.
Local risk profile
With 13,527 homes and around 26,885 residents, Union County is 514 square miles of northern South Carolina. The county seat is Union, and Monarch Mill, Buffalo and Jonesville round out the largest towns. The county's median home was built in 1972.
58/100 Water Damage Risk Index: Elevated Union County ranks 17 of 46 South Carolina counties. See the statewide ranking and method.The three factors where Union County ranks highest compared with other South Carolina counties.
Union is on the colder side of South Carolina for pipes. It averaged 53 freezing nights a year over 2015–2024, 3 of them at 20°F or colder, cold enough for pipes in outside walls and crawl spaces to freeze. Among 46 South Carolina counties that's 7th.
Most freezing nights fall from December to January, 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 Nov 10 and the last spring freeze around Mar 24.
Union gets fewer downpours than most South Carolina counties, but they still fill basements. The county gets about 47.3 inches of rain and melted snow a year, with 10.6 days of an inch or more (39th of 46). Those downpours cluster in April, November and December, when sump pumps and gutters are tested hardest. The wettest day on record brought 5.39 inches on September 27, 2024. Multi-day storms matter most for basements; the wettest three days on record here totaled 6.12 inches (through September 28, 2024).
The temperature crosses 32°F in both directions on roughly 52 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 64% of the county's housing was built before 1980. That puts Union among the oldest housing stocks of South Carolina's 46 counties.
In Union County 31% of homes are older than 1960. If yours is one of them and the plumbing has never been replaced, expect galvanized steel supply pipe and cast iron drain lines, the two materials most likely to fail quietly.
23% date from 1980 to 1999, the window when polybutylene, a gray flexible plastic supply pipe, was used in some homes. It's prone to leaks at the fittings, so it's worth checking for in a house from those years.
Manufactured and mobile homes make up 21% of the housing here. Water lines in the underbelly depend on intact skirting and working heat tape, and they're usually the first to freeze in a cold snap.
Beyond water
Union County averages 96 warm, muggy nights a year (lows of 65°F or more) and gets the most rain in December. 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 30% utility gas, 58% electric, 7% propane and 2% wood. Wood heat is 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 Union County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Cherokee and York get more pipe-freeze nights than Union. Its housing is the oldest in the area by share of homes built before 1980.
By the numbers
| Factor | Union | South Carolina median | Rank |
|---|---|---|---|
| Homes built before 1960 | 31% | 15% | 1 of 46 |
| Homes built before 1980 | 64% | 40% | 1 of 46 |
| Homes built 2000 or later | 13% | 25% | 44 of 46 |
| Manufactured or mobile homes | 21% | 22% | 26 of 46 |
| Vacant homes | 14% | 16% | 27 of 46 |
| Wood or propane heat | 9.3% | 5.1% | 13 of 46 |
| Nights at 20°F or colder | 3/yr | 2/yr | 7 of 46 |
| Days with 1 inch+ of rain | 11/yr | 12/yr | 39 of 46 |
| Freeze-thaw days | 52/yr | 35/yr | 4 of 46 |
| Muggy nights (65°F+) | 96/yr | 114/yr | 38 of 46 |
Rank 1 is the highest value. Bars run from the lowest to the highest South Carolina 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 December to January, heavy rain in April, November and December.
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