Washoe County, Nevada
Shrink-swell clay limits houses without basements on 34% of Washoe County's mapped land, a higher share than 83% of US counties and the highest of 17 Nevada counties. A shallow water table limits basements on 3%.
100% of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 146 flood losses here since 2016, 23% of them in buildings with basements. 35% of homes were built before 1980, against 50% nationally; the median home dates from 1991.
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 Washoe County
| Expansive clay (limits slab homes) | 33.9% |
| High water table (limits basements) | 3.4% |
| Septic fields very limited | 86.3% |
| Clay swell (LEP, by area) | 4.7% |
| High-swell land (LEP 6%+) | 34.6% |
| Mapped soil | 4,042,063 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Devada | 5% | n/a |
| Reywat | 3% | n/a |
| Old camp | 2% | n/a |
| Wylo | 2% | n/a |
| Bucklake | 2% | n/a |
| Ninemile | 2% | n/a |
How we count · survey areas CA685 (2025-09-05), CA693 (2025-09-02), NV603 (2025-08-28), NV628 (2025-08-29), NV759 (2025-09-02), NV771 (2025-09-02), NV792 (2025-09-02)
What the numbers mean here
Clay swell averages a linear extensibility of 4.7% by land area here, and 35% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 34% of the mapped land.
Clay shrinks as it dries: 100% of the county is in drought on the latest map, and 34% of Washoe County's mapped land has shrink-swell clay.
Rain over the 12 months to August 2026: 10.81 in, 1.66 in below the 1991-2020 average year of 12.47 in.
USDA rates 86% of the land very limited for septic absorption fields.
Drought
100% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 28 of the last 52 weeks; the most was 100% of its area, in 8 weeks, most recently on the October 13, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 100% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
146 flood losses since 2016, $3.2 million paid. The worst year was 2017, with 116. Foundations of the buildings, where recorded: 23% basements, 23% slabs, 47% crawl spaces, 7% elevated. Median water depth outside the building: 5 in.
| Year | Flood losses |
|---|---|
| 2016 | 4 |
| 2017 | 116 |
| 2018 | 4 |
| 2019 | 6 |
| 2020 | 0 |
| 2021 | 3 |
| 2022 | 3 |
| 2023 | 7 |
| 2024 | 1 |
| 2025 | 0 |
| 2026 to date | 2 |
Rain
| Average year, 1991-2020 | 12.47 in |
| 12 months to August 2026 | 10.81 in (-1.66) |
| 2025 | 13.86 in (+1.39) |
| Wettest year since 1895 | 1983: 22.46 in |
| Driest year since 1895 | 2013: 6.48 in |
| Days with 1 inch or more, normal at SMOKE CREEK ESPIL (10 mi away) | 0.8 |
Homes
| Housing units | 218,165 |
| Median year built | 1991 |
| Built before 1980 | 35% |
| Built 2000 or later | 35% |
| Owner-occupied | 60% |
| Median value, owner-occupied | $539,900 |
| Single-family detached | 59% |
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 |
|---|---|---|---|
| Lassen County, CA | 50 mi | 21% | 6% |
| Pershing County, NV | 69 mi | 11% | 4% |
| Plumas County, CA | 80 mi | 4% | 2% |
| Modoc County, CA | 81 mi | 27% | 15% |
| Storey County, NV | 90 mi | 30% | under 1% |
| Sierra County, CA | 92 mi | 5% | 9% |
| Humboldt County, NV | 93 mi | 21% | 9% |
| Carson City, NV | 109 mi | 11% | 5% |
Sources: USDA SSURGO (September 5, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status