Canyon County, Idaho
USDA's soil survey flags shrink-swell clay on 1% of Canyon County's mapped land and a shallow water table under basements on 14%, both below the national shares of 15% and 29%. 11.3% of the county is in drought on the October 13, 2026 Drought Monitor map.
FEMA's flood data list 8 flood losses here since 2016. 31% of homes were built before 1980, against 50% nationally; the median home dates from 1999.
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 Canyon County
| Expansive clay (limits slab homes) | 0.8% |
| High water table (limits basements) | 13.5% |
| Septic fields very limited | 68.4% |
| Clay swell (LEP, by area) | 2.6% |
| High-swell land (LEP 6%+) | 0.8% |
| Mapped soil | 371,241 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Power | 11% | n/a |
| Scism | 9% | n/a |
| Elijah | 7% | n/a |
| Turbyfill | 6% | n/a |
| Purdam | 5% | n/a |
| Greenleaf | 5% | n/a |
How we count · survey areas ID665 (2025-08-27)
What the numbers mean here
Rain over the 12 months to August 2026: 10.16 in, 0.61 in above the 1991-2020 average year of 9.55 in.
USDA rates 68% of the land very limited for septic absorption fields.
With shrink-swell clay on 1% and a shallow water table on 14% of the land, the soil survey points to neither problem across most of Canyon County; conditions still vary lot by lot.
Drought
11.3% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 18 of the last 52 weeks; the most was 11.3% of its area, in 18 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 | 11.3% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
8 flood losses since 2016, $59,539 paid. The worst year was 2017, with 4.
| Year | Flood losses |
|---|---|
| 2016 | 1 |
| 2017 | 4 |
| 2018 | 0 |
| 2019 | 0 |
| 2020 | 1 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 1 |
| 2025 | 0 |
| 2026 to date | 1 |
Rain
| Average year, 1991-2020 | 9.55 in |
| 12 months to August 2026 | 10.16 in (+0.61) |
| 2025 | 10.37 in (+0.82) |
| Wettest year since 1895 | 1983: 15.50 in |
| Driest year since 1895 | 1949: 4.86 in |
| Days with 1 inch or more, normal at EMMETT 2 E (20 mi away) | 0.3 |
Homes
| Housing units | 89,135 |
| Median year built | 1999 |
| Built before 1980 | 31% |
| Built 2000 or later | 49% |
| Owner-occupied | 76% |
| Median value, owner-occupied | $390,000 |
| Single-family detached | 79% |
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 |
|---|---|---|---|
| Payette County, ID | 26 mi | 4% | 9% |
| Ada County, ID | 26 mi | 20% | 4% |
| Gem County, ID | 34 mi | 19% | 9% |
| Malheur County, OR | 54 mi | 19% | 4% |
| Boise County, ID | 55 mi | 3% | 2% |
| Washington County, ID | 57 mi | 33% | 3% |
| Elmore County, ID | 64 mi | 7% | 2% |
| Owyhee County, ID | 77 mi | 27% | 2% |
Sources: USDA SSURGO (August 27, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status