Johnson County, Missouri
A shallow water table limits basements on 79% of Johnson County's mapped land, a higher share than 88% of US counties. Shrink-swell clay limits houses without basements on 41%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 13 flood losses here since 2016. 37% of homes were built before 1980, against 50% nationally; the median home dates from 1990.
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 Johnson County
| Expansive clay (limits slab homes) | 41.3% |
| High water table (limits basements) | 78.6% |
| Septic fields very limited | 99.4% |
| Clay swell (LEP, by area) | 6.0% |
| High-swell land (LEP 6%+) | 56.8% |
| Mapped soil | 533,485 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Sampsel | 19% | n/a |
| Deepwater | 10% | n/a |
| Snead | 8% | n/a |
| Mandeville | 6% | n/a |
| Haig | 5% | n/a |
| Nodaway | 5% | n/a |
How we count · survey areas MO101 (2025-09-02)
What the numbers mean here
Clay swell averages a linear extensibility of 6.0% by land area here, and 57% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 41% of the mapped land.
On 79% of Johnson 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: 42.14 in, 0.70 in above the 1991-2020 average year of 41.44 in.
USDA rates 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 13 of the last 52 weeks; the most was 100% of its area, in 5 weeks, most recently on the November 18, 2025 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 100% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
13 flood losses since 2016, $74,710 paid. The worst year was 2020, with 4.
| Year | Flood losses |
|---|---|
| 2016 | 2 |
| 2017 | 1 |
| 2018 | 0 |
| 2019 | 1 |
| 2020 | 4 |
| 2021 | 2 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 1 |
| 2025 | 2 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 41.44 in |
| 12 months to August 2026 | 42.14 in (+0.70) |
| 2025 | 35.66 in (-5.78) |
| Wettest year since 1895 | 1961: 59.72 in |
| Driest year since 1895 | 1956: 23.54 in |
| Days with 1 inch or more, normal at ELM (15 mi away) | 12.1 |
Homes
| Housing units | 22,731 |
| Median year built | 1990 |
| Built before 1980 | 37% |
| Built 2000 or later | 35% |
| Owner-occupied | 64% |
| Median value, owner-occupied | $235,700 |
| Single-family detached | 68% |
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 |
|---|---|---|---|
| Lafayette County, MO | 23 mi | 25% | 64% |
| Henry County, MO | 25 mi | 34% | 60% |
| Pettis County, MO | 28 mi | 68% | 76% |
| Cass County, MO | 30 mi | 68% | 80% |
| Jackson County, MO | 34 mi | 36% | 50% |
| Ray County, MO | 40 mi | 71% | 84% |
| Benton County, MO | 42 mi | 41% | 28% |
| Saline County, MO | 43 mi | 44% | 69% |
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