Onondaga County, New York
A shallow water table limits basements on 46% of Onondaga County's mapped land, a higher share than 63% of US counties. Shrink-swell clay limits houses without basements on 1%.
0.1% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 112 flood losses here since 2016, 59% of them in buildings with basements. 70% of homes were built before 1980, against 50% nationally; the median home dates from 1964.
Data as of October 13, 2026 · sources
expansive clay: shrink-swell limits slab homes
high water table: limits basements
in drought, October 13, 2026
of homes built before 1980
Soil under Onondaga County
| Expansive clay (limits slab homes) | 1.3% |
| High water table (limits basements) | 45.8% |
| Septic fields very limited | 66.8% |
| Clay swell (LEP, by area) | 2.2% |
| High-swell land (LEP 6%+) | 1.3% |
| Urban land, not rated | 1.1% |
| Mapped soil | 508,400 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Honeoye | 11% | n/a |
| Lansing | 5% | n/a |
| Ontario | 4% | n/a |
| Niagara | 4% | n/a |
| Palmyra | 3% | n/a |
| Lima | 3% | n/a |
How we count · survey areas NY067 (2025-09-02)
What the numbers mean here
On 46% of Onondaga County's mapped land, soil stays saturated within about 6 feet of the surface for part of the year, which is basement depth.
Rain over the 12 months to August 2026: 43.12 in, 0.44 in above the 1991-2020 average year of 42.68 in.
USDA rates 67% of the land very limited for septic absorption fields.
Drought
0.1% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 12 of the last 52 weeks; the most was 94% of its area, on the October 28, 2025 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 83.1% |
| D1 moderate drought or worse | 0.1% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
112 flood losses since 2016, $2.4 million paid. The worst year was 2021, with 45. Foundations of the buildings, where recorded: 59% basements, 19% slabs, 8% crawl spaces, 14% elevated. Median water depth outside the building: 9 in.
| Year | Flood losses |
|---|---|
| 2016 | 8 |
| 2017 | 8 |
| 2018 | 6 |
| 2019 | 7 |
| 2020 | 1 |
| 2021 | 45 |
| 2022 | 1 |
| 2023 | 18 |
| 2024 | 1 |
| 2025 | 11 |
| 2026 to date | 6 |
Rain
| Average year, 1991-2020 | 42.68 in |
| 12 months to August 2026 | 43.12 in (+0.44) |
| 2025 | 41.31 in (-1.37) |
| Wettest year since 1895 | 1972: 51.11 in |
| Driest year since 1895 | 1934: 28.74 in |
| Days with 1 inch or more, normal at SYRACUSE HANCOCK INTL AP (9 mi away) | 5.9 |
Homes
| Housing units | 212,002 |
| Median year built | 1964 |
| Built before 1980 | 70% |
| Built 2000 or later | 12% |
| Owner-occupied | 66% |
| Median value, owner-occupied | $200,200 |
| Single-family detached | 64% |
What repairs cost
Published ranges from cost guides, not quotes. More sources, and where they disagree.
Nearby counties
| Place | Distance | Expansive clay | High water table |
|---|---|---|---|
| Cayuga County, NY | 19 mi | 3% | 56% |
| Madison County, NY | 28 mi | 2% | 57% |
| Cortland County, NY | 29 mi | 0% | 62% |
| Oswego County, NY | 31 mi | 1% | 59% |
| Seneca County, NY | 35 mi | 11% | 57% |
| Tompkins County, NY | 41 mi | under 1% | 70% |
| Oneida County, NY | 42 mi | under 1% | 53% |
| Wayne County, NY | 45 mi | 1% | 56% |
Sources: USDA SSURGO (September 2, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status