Adair County, Iowa
Shrink-swell clay limits houses without basements on 91% of Adair County's mapped land, a higher share than 100% of US counties and the highest of 99 Iowa counties. A shallow water table limits basements on 80%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list no flood losses here since 2016. 77% of homes were built before 1980, against 50% nationally; the median home dates from 1958.
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 Adair County
| Expansive clay (limits slab homes) | 90.9% |
| High water table (limits basements) | 79.7% |
| Septic fields very limited | 98.4% |
| Clay swell (LEP, by area) | 6.2% |
| High-swell land (LEP 6%+) | 50.8% |
| Mapped soil | 364,600 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Sharpsburg | 24% | 98% |
| Shelby | 13% | n/a |
| Colo | 11% | n/a |
| Nira | 8% | n/a |
| Lamoni | 7% | n/a |
| Ely | 5% | n/a |
How we count · survey areas IA001 (2025-09-05)
What the numbers mean here
Clay swell averages a linear extensibility of 6.2% by land area here, and 51% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 91% of the mapped land.
On 80% of Adair 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: 34.60 in, 1.53 in below the 1991-2020 average year of 36.13 in.
USDA rates 98% 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 4 of the last 52 weeks; the most was 51.2% of its area, in 2 weeks, most recently on the August 4, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 0% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
FEMA's flood data list no flood losses in Adair County since 2016.
Rain
| Average year, 1991-2020 | 36.13 in |
| 12 months to August 2026 | 34.60 in (-1.53) |
| 2025 | 33.99 in (-2.14) |
| Wettest year since 1895 | 1973: 52.75 in |
| Driest year since 1895 | 1988: 19.04 in |
| Days with 1 inch or more, normal at GREENFIELD (3 mi away) | 9 |
Homes
| Housing units | 3,568 |
| Median year built | 1958 |
| Built before 1980 | 77% |
| Built 2000 or later | 11% |
| Owner-occupied | 74% |
| Median value, owner-occupied | $160,400 |
| Single-family detached | 87% |
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 |
|---|---|---|---|
| Cass County, IA | 24 mi | 49% | 46% |
| Union County, IA | 24 mi | 85% | 78% |
| Madison County, IA | 24 mi | 88% | 77% |
| Adams County, IA | 24 mi | 88% | 78% |
| Guthrie County, IA | 25 mi | 62% | 66% |
| Audubon County, IA | 33 mi | 30% | 29% |
| Dallas County, IA | 33 mi | 17% | 60% |
| Montgomery County, IA | 41 mi | 36% | 40% |
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