Onondaga County, New York · Syracuse
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Onondaga County averages 52 nights a year at 20°F or colder, mostly November to April, and 45% of its homes predate 1960.
Basements flood here mostly in September. Onondaga County averages 4.6 days a year with an inch of rain or more.
Backups often follow heavy rain, which Onondaga County gets about 4.6 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 90 freeze-thaw days a year, from winter ice dams. Most show up as ceiling stains in the room below.
4% of occupied homes in Onondaga County heat mainly with wood or propane, below the New York county median of 19%.
Muggy summer nights, lows of 65°F or more, come about 16 times a year in Onondaga County. Mold after a leak spreads fastest from June through August.
Local risk profile
Onondaga County covers 778 square miles of central New York, with about 471,129 residents and 212,002 homes. Syracuse is the county seat; De Witt, Fairmount and Baldwinsville are the next largest communities. The county's median home was built in 1964.
45/100 Water Damage Risk Index: Elevated Onondaga County ranks 37 of 57 New York counties. See the statewide ranking and method.The three factors where Onondaga County ranks highest compared with other New York counties.
For frozen pipes, Onondaga County is a typical New York county, which is still plenty. It averaged 134 freezing nights a year over 2015–2024, 52 of them at 20°F or colder, cold enough for pipes in outside walls and crawl spaces to freeze. Among 57 New York counties that's 35th.
Cold snaps are the real risk. The worst in the record lasted 32 days below freezing (ending March 2015), and the low bottomed out near -21°F on February 14, 2016.
Most freezing nights fall from November to April, 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 Oct 23 and the last spring freeze around May 7.
Onondaga gets fewer downpours than most New York counties, but they still fill basements. The county gets about 44.4 inches of rain and melted snow a year, with 4.6 days of an inch or more (40th of 57). Those downpours cluster in June, July and September, when sump pumps and gutters are tested hardest. The wettest day on record brought 3.19 inches on October 30, 2017. Multi-day storms matter most for basements; the wettest three days on record here totaled 5 inches (through October 23, 2016).
About 90 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
New York's 57 counties range widely in housing age; Onondaga ranks 18th, with 70% of its homes built before 1980.
The mix runs from 45% built before 1960 to 12% built since 2000, so older neighborhoods bring aging pipe while newer subdivisions bring failed appliance lines and water heaters.
Renters occupy 34% 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
Onondaga County averages 16 warm, muggy nights a year (lows of 65°F or more) and gets the most rain in October. 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, Onondaga County homes break down as 70% utility gas, 21% electric, 3% 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 Onondaga County. The largest communities by population:
Population from ACS 2020-2024 5-year estimates. Townships and unincorporated areas are covered too.
Nearby
Cortland, Madison and Oswego get more pipe-freeze nights than Onondaga. Cortland County has the oldest housing nearby, with 74% of homes built before 1980.
By the numbers
| Factor | Onondaga | New York median | Rank |
|---|---|---|---|
| Homes built before 1960 | 45% | 45% | 28 of 57 |
| Homes built before 1980 | 70% | 67% | 18 of 57 |
| Homes built 2000 or later | 12% | 13% | 40 of 57 |
| Manufactured or mobile homes | 1.1% | 7.6% | 51 of 57 |
| Vacant homes | 6.7% | 14% | 50 of 57 |
| Wood or propane heat | 4.3% | 19% | 51 of 57 |
| Nights at 20°F or colder | 52/yr | 55/yr | 35 of 57 |
| Days with 1 inch+ of rain | 4.6/yr | 6/yr | 40 of 57 |
| Freeze-thaw days | 90/yr | 101/yr | 42 of 57 |
| Muggy nights (65°F+) | 16/yr | 12/yr | 17 of 57 |
Rank 1 is the highest value. Bars run from the lowest to the highest New York county; the tick marks the median; orange means higher water damage risk than the median, green means lower.
Questions
Peak risk months in Onondaga County: freezing from November to April, 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