Ontario County, New York
A shallow water table limits basements on 59% of Ontario County's mapped land, a higher share than 73% of US counties. Shrink-swell clay limits houses without basements on 11%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 63 flood losses here since 2016, 69% of them in buildings with basements. 55% of homes were built before 1980, against 50% nationally; the median home dates from 1976.
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 Ontario County
| Expansive clay (limits slab homes) | 11.1% |
| High water table (limits basements) | 58.8% |
| Septic fields very limited | 84.4% |
| Clay swell (LEP, by area) | 2.6% |
| High-swell land (LEP 6%+) | 11.1% |
| Mapped soil | 423,800 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Lima | 9% | n/a |
| Honeoye | 8% | n/a |
| Schoharie | 6% | n/a |
| Palmyra | 6% | n/a |
| Ontario | 5% | n/a |
| Arkport | 4% | n/a |
How we count · survey areas NY069 (2025-09-02)
What the numbers mean here
On 59% of Ontario 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: 36.47 in, 0.65 in above the 1991-2020 average year of 35.82 in.
USDA rates 84% of the land very limited for septic absorption fields.
Drought
0% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 21 of the last 52 weeks; the most was 100% of its area, in 20 weeks, most recently on the March 3, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
63 flood losses since 2016, $866,575 paid. The worst year was 2023, with 26. Foundations of the buildings, where recorded: 69% basements, 7% slabs, 15% crawl spaces, 9% elevated. Median water depth outside the building: 15.5 in.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 11 |
| 2018 | 0 |
| 2019 | 2 |
| 2020 | 2 |
| 2021 | 12 |
| 2022 | 1 |
| 2023 | 26 |
| 2024 | 1 |
| 2025 | 4 |
| 2026 to date | 4 |
Rain
| Average year, 1991-2020 | 35.82 in |
| 12 months to August 2026 | 36.47 in (+0.65) |
| 2025 | 30.14 in (-5.68) |
| Wettest year since 1895 | 2017: 43.97 in |
| Driest year since 1895 | 1930: 24.71 in |
| Days with 1 inch or more, normal at CANANDAIGUA 3 S (1 mi away) | 5.7 |
Homes
| Housing units | 53,379 |
| Median year built | 1976 |
| Built before 1980 | 55% |
| Built 2000 or later | 22% |
| Owner-occupied | 74% |
| Median value, owner-occupied | $222,900 |
| Single-family detached | 67% |
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 |
|---|---|---|---|
| Yates County, NY | 18 mi | 1% | 83% |
| Seneca County, NY | 25 mi | 11% | 57% |
| Livingston County, NY | 26 mi | 24% | 78% |
| Wayne County, NY | 28 mi | 1% | 56% |
| Monroe County, NY | 34 mi | 6% | 55% |
| Schuyler County, NY | 35 mi | 2% | 62% |
| Cayuga County, NY | 38 mi | 3% | 56% |
| Steuben County, NY | 41 mi | 0% | 63% |
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