Tompkins County, New York
A shallow water table limits basements on 70% of Tompkins County's mapped land, a higher share than 82% of US counties and the 8th highest of 62 New York counties. Shrink-swell clay limits houses without basements on under 1%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 19 flood losses here since 2016. 57% of homes were built before 1980, against 50% nationally; the median home dates from 1974.
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 Tompkins County
| Expansive clay (limits slab homes) | under 0.1% |
| High water table (limits basements) | 70.0% |
| Septic fields very limited | 86.3% |
| Clay swell (LEP, by area) | 1.8% |
| High-swell land (LEP 6%+) | under 0.1% |
| Mapped soil | 310,952 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Erie | 9% | n/a |
| Langford | 9% | n/a |
| Lordstown | 9% | n/a |
| Bath | 8% | n/a |
| Volusia | 7% | over 99% |
| Mardin | 6% | n/a |
How we count · survey areas NY109 (2025-09-02)
What the numbers mean here
On 70% of Tompkins 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: 39.07 in, 0.86 in below the 1991-2020 average year of 39.93 in.
USDA rates 86% 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 2 of the last 52 weeks; the most was 67% of its area, on the October 21, 2025 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 0.1% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
19 flood losses since 2016, $104,065 paid. The worst year was 2017, with 8.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 8 |
| 2018 | 2 |
| 2019 | 2 |
| 2020 | 1 |
| 2021 | 4 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 1 |
| 2025 | 0 |
| 2026 to date | 1 |
Rain
| Average year, 1991-2020 | 39.93 in |
| 12 months to August 2026 | 39.07 in (-0.86) |
| 2025 | 35.74 in (-4.19) |
| Wettest year since 1895 | 2011: 51.21 in |
| Driest year since 1895 | 1965: 27.69 in |
| Days with 1 inch or more, normal at ITHACA CORNELL UNIV (1 mi away) | 6.6 |
Homes
| Housing units | 47,804 |
| Median year built | 1974 |
| Built before 1980 | 57% |
| Built 2000 or later | 17% |
| Owner-occupied | 54% |
| Median value, owner-occupied | $290,900 |
| Single-family detached | 50% |
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 |
|---|---|---|---|
| Tioga County, NY | 21 mi | 0% | 56% |
| Cortland County, NY | 22 mi | 0% | 62% |
| Schuyler County, NY | 24 mi | 2% | 62% |
| Chemung County, NY | 25 mi | 0% | 49% |
| Seneca County, NY | 29 mi | 11% | 57% |
| Yates County, NY | 35 mi | 1% | 83% |
| Broome County, NY | 39 mi | 0% | 69% |
| Cayuga County, NY | 39 mi | 3% | 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