Sac County, Iowa
A shallow water table limits basements on 63% of Sac County's mapped land, a higher share than 77% of US counties. Shrink-swell clay limits houses without basements on 26%.
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 1957.
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 Sac County
| Expansive clay (limits slab homes) | 25.7% |
| High water table (limits basements) | 63.4% |
| Septic fields very limited | 90.6% |
| Clay swell (LEP, by area) | 4.5% |
| High-swell land (LEP 6%+) | 15.9% |
| Mapped soil | 370,100 acres |
How we count · survey areas IA161 (2025-09-09)
What the numbers mean here
Clay swell averages a linear extensibility of 4.5% by land area here, and 16% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 26% of the mapped land.
On 63% of Sac 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: 22.71 in, 9.42 in below the 1991-2020 average year of 32.13 in.
USDA rates 91% 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 3 weeks, most recently on the August 11, 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 Sac County since 2016.
Rain
| Average year, 1991-2020 | 32.13 in |
| 12 months to August 2026 | 22.71 in (-9.42) |
| 2025 | 32.28 in (+0.15) |
| Wettest year since 1895 | 1951: 45.35 in |
| Driest year since 1895 | 1976: 16.78 in |
| Days with 1 inch or more, normal at SAC CITY (7 mi away) | 7.8 |
Homes
| Housing units | 5,118 |
| Median year built | 1957 |
| Built before 1980 | 81% |
| Built 2000 or later | 9% |
| Owner-occupied | 78% |
| Median value, owner-occupied | $141,400 |
| Single-family detached | 84% |
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 |
|---|---|---|---|
| Ida County, IA | 21 mi | 23% | 27% |
| Calhoun County, IA | 24 mi | 13% | 91% |
| Buena Vista County, IA | 25 mi | 22% | 83% |
| Carroll County, IA | 27 mi | 18% | 41% |
| Crawford County, IA | 28 mi | 12% | 15% |
| Pocahontas County, IA | 32 mi | 13% | 93% |
| Cherokee County, IA | 36 mi | 27% | 36% |
| Greene County, IA | 44 mi | 11% | 71% |
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