Pinal County, Arizona
Shrink-swell clay limits houses without basements on 15% of Pinal County's mapped land, a higher share than 64% of US counties and the 7th highest of 15 Arizona counties. A shallow water table limits basements on under 1%.
26.1% of the county is in drought on the October 13, 2026 Drought Monitor map, down from 37.4% a week earlier. FEMA's flood data list 34 flood losses here since 2016, 0% of them in buildings with basements. 14% of homes were built before 1980, against 50% nationally; the median home dates from 2004.
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 Pinal County
| Expansive clay (limits slab homes) | 15.3% |
| High water table (limits basements) | 0.4% |
| Septic fields very limited | 59.0% |
| Clay swell (LEP, by area) | 3.4% |
| High-swell land (LEP 6%+) | 14.1% |
| Mapped soil | 3,266,569 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Denure | 7% | n/a |
| Mohall | 6% | n/a |
| Casa Grande | 4% | n/a |
| Dateland | 3% | n/a |
| Glenbar | 2% | n/a |
| Romero | 2% | n/a |
How we count · survey areas AZ645 (2025-08-28), AZ655 (2025-08-27), AZ658 (2025-08-27), AZ659 (2025-08-27), AZ661 (2025-08-27), AZ675 (2025-08-27), AZ687 (2025-08-27), AZ703 (2025-08-27)
What the numbers mean here
Clay swell averages a linear extensibility of 3.4% by land area here, and 14% of the land reaches USDA's high class (6% or more). Clay like that swells when wet and shrinks when dry, under 15% of the mapped land.
Clay shrinks as it dries: 26.1% of the county is in drought on the latest map, and 15% of Pinal County's mapped land has shrink-swell clay.
Rain over the 12 months to August 2026: 10.18 in, 1.08 in below the 1991-2020 average year of 11.26 in.
USDA rates 59% of the land very limited for septic absorption fields.
Drought
26.1% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 52 of the last 52 weeks; the most was 100% of its area, in 15 weeks, most recently on the July 21, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 99.7% |
| D1 moderate drought or worse | 26.1% |
| D2 severe or worse | 8.3% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
34 flood losses since 2016, $1.9 million paid. The worst year was 2017, with 7. Foundations of the buildings, where recorded: 77% slabs, 23% crawl spaces.
| Year | Flood losses |
|---|---|
| 2016 | 4 |
| 2017 | 7 |
| 2018 | 4 |
| 2019 | 6 |
| 2020 | 0 |
| 2021 | 1 |
| 2022 | 5 |
| 2023 | 3 |
| 2024 | 2 |
| 2025 | 2 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 11.26 in |
| 12 months to August 2026 | 10.18 in (-1.08) |
| 2025 | 9.07 in (-2.19) |
| Wettest year since 1895 | 1905: 23.96 in |
| Driest year since 1895 | 2020: 4.96 in |
| Days with 1 inch or more, normal at CASA GRANDE NM (11 mi away) | 1.3 |
Homes
| Housing units | 184,651 |
| Median year built | 2004 |
| Built before 1980 | 14% |
| Built 2000 or later | 65% |
| Owner-occupied | 82% |
| Median value, owner-occupied | $349,000 |
| 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 |
|---|---|---|---|
| Pima County, AZ | 60 mi | 9% | 0% |
| Gila County, AZ | 68 mi | 30% | under 1% |
| Maricopa County, AZ | 72 mi | 3% | 1% |
| Graham County, AZ | 86 mi | 32% | under 1% |
| Santa Cruz County, AZ | 101 mi | 16% | 0% |
| Cochise County, AZ | 119 mi | 28% | under 1% |
| Greenlee County, AZ | 125 mi | 35% | 1% |
| Yavapai County, AZ | 139 mi | 29% | under 1% |
Sources: USDA SSURGO (August 28, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status