Fairfax County, Virginia · Fairfax
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Pipes freeze in Fairfax County on about 12 nights a year, mostly December to February. Older homes, 11% of the stock here, are most at risk.
Basements flood here mostly in July. Fairfax County averages 8.8 days a year with an inch of rain or more.
Sewage backups in Fairfax County spike on heavy-rain days, about 8.8 a year, when sewer mains fill up and water finds the lowest drain.
Fairfax County's wettest day in the 2015–2024 record brought 4.51 inches, and about 67 freeze-thaw days a year mean ice dams in some winters.
2% of occupied homes in Fairfax County heat mainly with wood or propane, below the Virginia county median of 11.9%.
About 75 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
Fairfax County covers 391 square miles of northeast Virginia, with about 1,147,837 residents and 430,047 homes. Fairfax is the county seat; Centreville, Reston and McLean are the next largest communities. The county's median home was built in 1983.
34/100 Water Damage Risk Index: Moderate Fairfax County ranks 88 of 95 Virginia counties. See the statewide ranking and method.The three factors where Fairfax County ranks highest compared with other Virginia counties.
For frozen pipes, Fairfax County is a typical Virginia county, which is still plenty. From 2015–2024 it averaged 12 nights a year at 20°F or colder, the range where pipes in exterior walls, crawl spaces and unheated garages freeze, and 73 nights at or below 32°F. That ranks 55th of 95 counties.
Cold snaps are the real risk. The worst in the record lasted 7 days below freezing (ending January 2018), and the low bottomed out near 2°F on February 20, 2015.
The freeze season here runs December to February, with January the coldest. If you travel then, leave the thermostat at 55°F or above and open sink cabinets on outside walls.
On average the first fall freeze arrives around Nov 11 and the last spring freeze around Mar 29.
Fairfax gets fewer downpours than most Virginia counties, but they still fill basements. About 8.8 days a year bring an inch or more (66th of 95), most often in July, out of 42.2 inches of total precipitation. On July 22, 2018, 4.51 inches fell in a single day. Multi-day storms matter most for basements; the wettest three days on record here totaled 6.55 inches (through July 24, 2018).
The temperature crosses 32°F in both directions on roughly 67 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
Virginia's 95 counties range widely in housing age; Fairfax ranks 54th, with 44% of its homes built before 1980.
Housing age is mixed: 11% of homes are pre-1960 and 20% are 2000 or newer. Ask any plumber which era your house is from and you'll know which failures to watch for.
The 1980s and 1990s account for 37% 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.
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
Fairfax County averages 75 warm, muggy nights a year (lows of 65°F or more) and gets the most rain in July. 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 expectHeating fuel matters for fire risk. In Fairfax County it's 54% utility gas, 42% electric, 1% propane and under 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 Fairfax County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Loudoun and Prince William get more pipe-freeze nights than Fairfax. Arlington County has the oldest housing nearby, with 53% of homes built before 1980.
By the numbers
| Factor | Fairfax | Virginia median | Rank |
|---|---|---|---|
| Homes built before 1960 | 11% | 20% | 80 of 95 |
| Homes built before 1980 | 44% | 46% | 54 of 95 |
| Homes built 2000 or later | 20% | 25% | 70 of 95 |
| Manufactured or mobile homes | 0.5% | 9.6% | 91 of 95 |
| Vacant homes | 3.7% | 15% | 93 of 95 |
| Wood or propane heat | 1.5% | 12% | 94 of 95 |
| Nights at 20°F or colder | 12/yr | 14/yr | 55 of 95 |
| Days with 1 inch+ of rain | 8.8/yr | 10/yr | 66 of 95 |
| Freeze-thaw days | 67/yr | 77/yr | 77 of 95 |
| Muggy nights (65°F+) | 75/yr | 64/yr | 33 of 95 |
Rank 1 is the highest value. Bars run from the lowest to the highest Virginia county; the tick marks the median; orange means higher water damage risk than the median, green means lower.
Questions
Peak risk months in Fairfax County: freezing from December to February, heavy rain in June, July and October.
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