Plymouth County, Iowa
A shallow water table limits basements on 27% of Plymouth County's mapped land. Shrink-swell clay limits houses without basements on 8%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 9 flood losses here since 2016. 63% 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 Plymouth County
| Expansive clay (limits slab homes) | 8.2% |
| High water table (limits basements) | 26.9% |
| Septic fields very limited | 82.6% |
| Clay swell (LEP, by area) | 4.3% |
| High-swell land (LEP 6%+) | 4.6% |
| Mapped soil | 553,000 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Galva | 46% | n/a |
| Ida | 15% | n/a |
| Radford | 9% | n/a |
| Monona | 5% | n/a |
| Kennebec | 4% | n/a |
| Primghar | 4% | n/a |
How we count · survey areas IA149 (2025-09-09)
What the numbers mean here
On 27% of Plymouth 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: 21.57 in, 8.26 in below the 1991-2020 average year of 29.83 in.
USDA rates 83% 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 49 of the last 52 weeks; the most was 100% of its area, in 10 weeks, most recently on the September 1, 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
9 flood losses since 2016, $379,678 paid. The worst year was 2024, with 6.
| Year | Flood losses |
|---|---|
| 2016 | 0 |
| 2017 | 1 |
| 2018 | 1 |
| 2019 | 0 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 0 |
| 2023 | 0 |
| 2024 | 6 |
| 2025 | 1 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 29.83 in |
| 12 months to August 2026 | 21.57 in (-8.26) |
| 2025 | 31.26 in (+1.43) |
| Wettest year since 1895 | 1951: 40.78 in |
| Driest year since 1895 | 1976: 14.47 in |
| Days with 1 inch or more, normal at LE MARS (5 mi away) | 7.3 |
Homes
| Housing units | 10,891 |
| Median year built | 1971 |
| Built before 1980 | 63% |
| Built 2000 or later | 16% |
| Owner-occupied | 74% |
| Median value, owner-occupied | $228,900 |
| 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 |
|---|---|---|---|
| Union County, SD | 23 mi | 33% | 42% |
| Sioux County, IA | 24 mi | 26% | 35% |
| Woodbury County, IA | 25 mi | 16% | 25% |
| Cherokee County, IA | 30 mi | 27% | 36% |
| Dakota County, NE | 30 mi | 13% | 22% |
| Dixon County, NE | 37 mi | 2% | 9% |
| O'Brien County, IA | 38 mi | 47% | 64% |
| Clay County, SD | 41 mi | 29% | 53% |
Sources: USDA SSURGO (September 9, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status