Shelby County, Missouri
A shallow water table limits basements on 91% of Shelby County's mapped land, a higher share than 96% of US counties and the 7th highest of 115 Missouri counties. Shrink-swell clay limits houses without basements on 87%.
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. 65% of homes were built before 1980, against 50% nationally; the median home dates from 1971.
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 Shelby County
| Expansive clay (limits slab homes) | 87.5% |
| High water table (limits basements) | 91.0% |
| Septic fields very limited | 99.6% |
| Clay swell (LEP, by area) | 9.2% |
| High-swell land (LEP 6%+) | 85.9% |
| Mapped soil | 321,370 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Mexico | 22% | n/a |
| Putnam | 15% | n/a |
| Leonard | 14% | n/a |
| Armstrong | 9% | over 99% |
| Keswick | 9% | n/a |
| Lindley | 7% | n/a |
How we count · survey areas MO205 (2025-09-02)
What the numbers mean here
Clay swell averages a linear extensibility of 9.2% by land area here, and 86% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 87% of the mapped land.
On 91% of Shelby 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: 37.11 in, 4.15 in below the 1991-2020 average year of 41.26 in.
USDA rates over 99% 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 22 of the last 52 weeks; the most was 100% of its area, in 9 weeks, most recently on the March 10, 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 Shelby County since 2016.
Rain
| Average year, 1991-2020 | 41.26 in |
| 12 months to August 2026 | 37.11 in (-4.15) |
| 2025 | 31.91 in (-9.35) |
| Wettest year since 1895 | 2008: 60.75 in |
| Driest year since 1895 | 1988: 19.46 in |
| Days with 1 inch or more, normal at SHELBINA (8 mi away) | 12 |
Homes
| Housing units | 2,950 |
| Median year built | 1971 |
| Built before 1980 | 65% |
| Built 2000 or later | 17% |
| Owner-occupied | 78% |
| Median value, owner-occupied | $99,900 |
| Single-family detached | 77% |
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 |
|---|---|---|---|
| Monroe County, MO | 21 mi | 84% | 85% |
| Knox County, MO | 24 mi | 81% | 85% |
| Marion County, MO | 24 mi | 53% | 69% |
| Macon County, MO | 25 mi | 80% | 95% |
| Lewis County, MO | 28 mi | 63% | 81% |
| Randolph County, MO | 33 mi | 83% | 85% |
| Ralls County, MO | 34 mi | 56% | 75% |
| Adair County, MO | 38 mi | 68% | 95% |
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