Montgomery County, Maryland · Rockville
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Pipes freeze in Montgomery County on about 15 nights a year, mostly December to March. Older homes, 20% of the stock here, are most at risk.
July brings the most downpours to Montgomery County, part of 8.4 heavy-rain days a year. Check the sump first.
Sewage backups in Montgomery County spike on heavy-rain days, about 8.4 a year, when sewer mains fill up and water finds the lowest drain.
Montgomery County's wettest day in the 2015–2024 record brought 4.29 inches, and about 72 freeze-thaw days a year mean ice dams in some winters.
2% of occupied homes in Montgomery County heat mainly with wood or propane, below the Maryland county median of 9.3%.
Muggy summer nights, lows of 65°F or more, come about 62 times a year in Montgomery County. Mold after a leak spreads fastest from June through August.
Local risk profile
Montgomery County covers 493 square miles of northern Maryland, with about 1,065,949 residents and 406,531 homes. Rockville is the county seat; Germantown, Silver Spring and Gaithersburg are the next largest communities. The county's median home was built in 1980.
43/100 Water Damage Risk Index: Moderate Montgomery County ranks 18 of 23 Maryland counties. See the statewide ranking and method.The three factors where Montgomery County ranks highest compared with other Maryland counties.
For frozen pipes, Montgomery County is a typical Maryland county, which is still plenty. It averaged 81 freezing nights a year over 2015–2024, 15 of them at 20°F or colder, cold enough for pipes in outside walls and crawl spaces to freeze. Among 23 Maryland counties that's 10th.
The longest cold spell was straight 7 days without the temperature rising above freezing, ending in January 2018. The coldest night reached about 2°F on February 20, 2015. Burst pipes usually show up when a spell like that breaks and the ice thaws.
Most freezing nights fall from December to March, 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 8 and the last spring freeze around Apr 4.
Montgomery gets fewer downpours than most Maryland counties, but they still fill basements. The county gets about 43.6 inches of rain and melted snow a year, with 8.4 days of an inch or more (18th of 23). Those downpours cluster in June, July and September, when sump pumps and gutters are tested hardest. The wettest day on record brought 4.29 inches on July 22, 2018. Multi-day storms matter most for basements; the wettest three days on record here totaled 6.18 inches (through July 24, 2018).
Freeze-thaw days, below freezing overnight and above it by afternoon, come about 72 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
Maryland's 23 counties range widely in housing age; Montgomery ranks 7th, with 49% of its homes built before 1980.
Housing age is mixed: 20% of homes are pre-1960 and 21% 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 30% 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 35% 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
Montgomery County averages 62 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 expectBy main heating fuel, Montgomery County homes break down as 53% utility gas, 41% electric, 2% 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 Montgomery County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Frederick and Howard get more pipe-freeze nights than Montgomery. Prince George's County has the oldest housing nearby, with 54% of homes built before 1980.
By the numbers
| Factor | Montgomery | Maryland median | Rank |
|---|---|---|---|
| Homes built before 1960 | 20% | 20% | 12 of 23 |
| Homes built before 1980 | 49% | 44% | 7 of 23 |
| Homes built 2000 or later | 21% | 23% | 17 of 23 |
| Manufactured or mobile homes | 0.2% | 2.6% | 23 of 23 |
| Vacant homes | 4.3% | 7.7% | 19 of 23 |
| Wood or propane heat | 1.9% | 9.3% | 22 of 23 |
| Nights at 20°F or colder | 15/yr | 12/yr | 10 of 23 |
| Days with 1 inch+ of rain | 8.4/yr | 9.3/yr | 18 of 23 |
| Freeze-thaw days | 72/yr | 70/yr | 11 of 23 |
| Muggy nights (65°F+) | 62/yr | 76/yr | 16 of 23 |
Rank 1 is the highest value. Bars run from the lowest to the highest Maryland county; the tick marks the median; orange means higher water damage risk than the median, green means lower.
Questions
Peak risk months in Montgomery County: freezing from December 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