Johnston County, North Carolina · Smithfield
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Johnston County averages 4 nights a year at 20°F or colder, mostly January, and 10% of its homes predate 1960.
Basements flood here mostly in September. Johnston County averages 11.4 days a year with an inch of rain or more.
Backups often follow heavy rain, which Johnston County gets about 11.4 days a year, when storm water overloads sewer mains and pushes up through the lowest drain in the house.
Roof leaks here come from summer downpours and, with about 47 freeze-thaw days a year, from winter ice dams. Most show up as ceiling stains in the room below.
8% of occupied homes in Johnston County heat mainly with wood or propane, below the North Carolina county median of 11.7%.
About 97 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 91,218 homes and around 234,263 residents, Johnston County is 792 square miles of eastern North Carolina. Besides Smithfield, the county seat, the biggest communities are Clayton, Selma and Archer Lodge. Much of its housing is recent, with a median build year of 2000.
35/100 Water Damage Risk Index: Moderate Johnston County ranks 89 of 100 North Carolina counties. See the statewide ranking and method.The three factors where Johnston County ranks highest compared with other North Carolina counties.
For frozen pipes, Johnston County is a typical North Carolina county, which is still plenty. From 2015–2024 it averaged 4 nights a year at 20°F or colder, the range where pipes in exterior walls, crawl spaces and unheated garages freeze, and 48 nights at or below 32°F. That ranks 58th of 100 counties.
On January 7, 2018 the low fell to about 7°F, and in the stretch ending January 2018 the county went 3 days in a row below freezing. Leaks from split pipes typically appear the day the thaw arrives.
Most freezing nights fall from 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 17 and the last spring freeze around Mar 21.
Rainfall is about average for North Carolina. The county gets about 52.5 inches of rain and melted snow a year, with 11.4 days of an inch or more (54th of 100). Those downpours cluster in July, September and December, when sump pumps and gutters are tested hardest. The wettest day on record brought 5.31 inches on October 9, 2016. Multi-day storms matter most for basements; the wettest three days on record here totaled 8.76 inches (through September 17, 2018).
About 47 days a year swing from below freezing at night to above freezing by day. Those freeze-thaw cycles feed ice dams on roofs, open cracks in foundations and driveways, and stress pipes that are already marginal.
Housing
North Carolina's 100 counties range widely in housing age; Johnston ranks 93rd, with 22% of its homes built before 1980.
50% of homes were built in 2000 or later, more than in most of North Carolina. Newer plumbing rarely corrodes, so damage here tends to come from appliance supply lines, water heaters, sump pumps and storms.
The 1980s and 1990s account for 28% 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.
Manufactured and mobile homes make up 13% 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
Johnston County averages 97 warm, muggy nights a year (lows of 65°F or more) and gets the most rain in September. Mold grows when indoor humidity stays above about 60%, the EPA's ceiling. A basement dehumidifier set to 50% and drying anything wet within 24 to 48 hours prevents most problems.
Mold remediation: what to expectMain heating fuel in Johnston County's occupied homes: 12% utility gas, 78% electric, 8% propane and under 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 Johnston County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Nash, Wake and Wilson get more pipe-freeze nights than Johnston. Wayne County has the oldest housing nearby, with 44% of homes built before 1980.
By the numbers
| Factor | Johnston | North Carolina median | Rank |
|---|---|---|---|
| Homes built before 1960 | 10% | 18% | 88 of 100 |
| Homes built before 1980 | 22% | 41% | 93 of 100 |
| Homes built 2000 or later | 50% | 26% | 3 of 100 |
| Manufactured or mobile homes | 13% | 17% | 73 of 100 |
| Vacant homes | 6.2% | 13% | 99 of 100 |
| Wood or propane heat | 8.2% | 12% | 71 of 100 |
| Nights at 20°F or colder | 4/yr | 5/yr | 58 of 100 |
| Days with 1 inch+ of rain | 11/yr | 12/yr | 54 of 100 |
| Freeze-thaw days | 47/yr | 57/yr | 63 of 100 |
| Muggy nights (65°F+) | 97/yr | 89/yr | 37 of 100 |
Rank 1 is the highest value. Bars run from the lowest to the highest North Carolina county; the tick marks the median; orange means higher water damage risk than the median, green means lower.
Questions
Peak risk months in Johnston County: freezing from January, heavy rain in July, September 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