Calhoun County, Iowa
A shallow water table limits basements on 91% of Calhoun County's mapped land, a higher share than 97% of US counties and the 2nd highest of 99 Iowa counties. Shrink-swell clay limits houses without basements on 13%.
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. 81% 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 Calhoun County
| Expansive clay (limits slab homes) | 12.8% |
| High water table (limits basements) | 91.3% |
| Septic fields very limited | 93.1% |
| Clay swell (LEP, by area) | 4.3% |
| High-swell land (LEP 6%+) | 10.2% |
| Mapped soil | 366,800 acres |
How we count · survey areas IA025 (2025-09-08)
What the numbers mean here
On 91% of Calhoun 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: 24.83 in, 8.48 in below the 1991-2020 average year of 33.31 in.
USDA rates 93% 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 10 of the last 52 weeks; the most was 85.8% of its area, 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 Calhoun County since 2016.
Rain
| Average year, 1991-2020 | 33.31 in |
| 12 months to August 2026 | 24.83 in (-8.48) |
| 2025 | 33.48 in (+0.17) |
| Wettest year since 1895 | 1973: 47.30 in |
| Driest year since 1895 | 1976: 18.68 in |
| Days with 1 inch or more, normal at ROCKWELL CITY (1 mi away) | 7.7 |
Homes
| Housing units | 4,798 |
| Median year built | 1958 |
| Built before 1980 | 81% |
| Built 2000 or later | 8% |
| Owner-occupied | 81% |
| Median value, owner-occupied | $118,800 |
| Single-family detached | 86% |
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 |
|---|---|---|---|
| Sac County, IA | 24 mi | 26% | 63% |
| Webster County, IA | 24 mi | 27% | 88% |
| Pocahontas County, IA | 24 mi | 13% | 93% |
| Carroll County, IA | 27 mi | 18% | 41% |
| Greene County, IA | 27 mi | 11% | 71% |
| Buena Vista County, IA | 35 mi | 22% | 83% |
| Humboldt County, IA | 35 mi | 10% | 90% |
| Boone County, IA | 43 mi | 9% | 64% |
Sources: USDA SSURGO (September 8, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status