Jefferson County, New York
A shallow water table limits basements on 47% of Jefferson County's mapped land, a higher share than 64% of US counties. Shrink-swell clay limits houses without basements on 15%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 92 flood losses here since 2016, 26% of them in buildings with basements. 56% of homes were built before 1980, against 50% nationally; the median home dates from 1972.
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 Jefferson County
| Expansive clay (limits slab homes) | 15.1% |
| High water table (limits basements) | 46.7% |
| Septic fields very limited | 75.4% |
| Clay swell (LEP, by area) | 3.3% |
| High-swell land (LEP 6%+) | 15.3% |
| Mapped soil | 883,400 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Rhinebeck | 4% | n/a |
| Galoo | 4% | n/a |
| Galway | 4% | n/a |
| Chaumont | 4% | n/a |
| Kingsbury | 3% | n/a |
| Hudson | 3% | n/a |
How we count · survey areas NY045 (2025-09-04)
What the numbers mean here
Clay swell averages a linear extensibility of 3.3% by land area here, and 15% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 15% of the mapped land.
On 47% of Jefferson 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: 47.57 in, 5.14 in above the 1991-2020 average year of 42.43 in.
USDA rates 75% 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 12 of the last 52 weeks; the most was 100% of its area, in 2 weeks, most recently on the October 28, 2025 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 6.8% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
92 flood losses since 2016, $1.6 million paid. The worst year was 2017, with 45. Foundations of the buildings, where recorded: 26% basements, 23% slabs, 26% crawl spaces, 26% elevated. Median water depth outside the building: 15 in.
| Year | Flood losses |
|---|---|
| 2016 | 1 |
| 2017 | 45 |
| 2018 | 4 |
| 2019 | 34 |
| 2020 | 4 |
| 2021 | 1 |
| 2022 | 1 |
| 2023 | 1 |
| 2024 | 0 |
| 2025 | 0 |
| 2026 to date | 1 |
Rain
| Average year, 1991-2020 | 42.43 in |
| 12 months to August 2026 | 47.57 in (+5.14) |
| 2025 | 42.77 in (+0.34) |
| Wettest year since 1895 | 2017: 53.94 in |
| Driest year since 1895 | 1934: 28.80 in |
| Days with 1 inch or more, normal at WATERTOWN INTL AP (2 mi away) | 5.4 |
Homes
| Housing units | 61,862 |
| Median year built | 1972 |
| Built before 1980 | 56% |
| Built 2000 or later | 22% |
| Owner-occupied | 55% |
| Median value, owner-occupied | $188,200 |
| Single-family detached | 57% |
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 |
|---|---|---|---|
| Lewis County, NY | 34 mi | under 1% | 50% |
| Oswego County, NY | 38 mi | 1% | 59% |
| St. Lawrence County, NY | 59 mi | 11% | 49% |
| Oneida County, NY | 61 mi | under 1% | 53% |
| Herkimer County, NY | 67 mi | under 1% | 45% |
| Onondaga County, NY | 69 mi | 1% | 46% |
| Cayuga County, NY | 73 mi | 3% | 56% |
| Wayne County, NY | 73 mi | 1% | 56% |
Sources: USDA SSURGO (September 4, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status