Hawaii County, Hawaii
USDA's soil survey flags shrink-swell clay on 4% of Hawaii County's mapped land and a shallow water table under basements on 4%, both below the national shares of 15% and 29%. None of the county is in drought on the November 3, 2026 Drought Monitor map.
FEMA's flood data list 85 flood losses here since 2016, 0% of them in buildings with basements. 34% of homes were built before 1980, against 50% nationally; the median home dates from 1989.
Data as of November 3, 2026 · sources
expansive clay: shrink-swell limits slab homes
high water table: limits basements
in drought, November 3, 2026
of homes built before 1980
Soil under Hawaii County
| Expansive clay (limits slab homes) | 3.6% |
| High water table (limits basements) | 4.0% |
| Septic fields very limited | 94.9% |
| Clay swell (LEP, by area) | 2.8% |
| High-swell land (LEP 6%+) | 3.6% |
| Mapped soil | 2,580,035 acres |
| Soil series | Share here | Series nationally: expansive clay |
|---|---|---|
| Kaiwiki | 3% | n/a |
| Keei | 2% | n/a |
| Honokaa | 2% | n/a |
| Waimea | 2% | n/a |
| Keaukaha | 2% | n/a |
| Kekake | 2% | n/a |
How we count · survey areas HI701 (2025-09-09), HI801 (2025-09-09)
What the numbers mean here
Rain over the 12 months to August 2026: 89.66 in, 26.37 in above the 1991-2020 average year of 63.29 in.
USDA rates 95% of the land very limited for septic absorption fields.
With shrink-swell clay on 4% and a shallow water table on 4% of the land, the soil survey points to neither problem across most of Hawaii County; conditions still vary lot by lot.
Drought
0% of the county is in drought (D1 or worse) on the November 3, 2026 map. Part of the county was in drought in 25 of the last 52 weeks; the most was 81.8% of its area, in 6 weeks, most recently on the January 6, 2026 map.
| Category, November 3, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 17.3% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
85 flood losses since 2016, $4.8 million paid. The worst year was 2026, with 23. Foundations of the buildings, where recorded: 58% slabs, 3% crawl spaces, 39% elevated. Median water depth outside the building: 11 in.
| Year | Flood losses |
|---|---|
| 2016 | 5 |
| 2017 | 1 |
| 2018 | 17 |
| 2019 | 3 |
| 2020 | 3 |
| 2021 | 2 |
| 2022 | 16 |
| 2023 | 1 |
| 2024 | 9 |
| 2025 | 5 |
| 2026 to date | 23 |
Rain
| Average year, 1991-2020 | 63.29 in |
| 12 months to August 2026 | 89.66 in (+26.37) |
| 2025 | 40.64 in (-22.65) |
| Wettest year since 1991 | 2018: 104.71 in |
| Driest year since 1991 | 2010: 36.51 in |
| Days with 1 inch or more, normal at PAPAIKOU MAUKA NO.2 140.4 (29 mi away) | 43.1 |
Homes
| Housing units | 90,735 |
| Median year built | 1989 |
| Built before 1980 | 34% |
| Built 2000 or later | 31% |
| Owner-occupied | 74% |
| Median value, owner-occupied | $519,300 |
| 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 |
|---|---|---|---|
| Maui County, HI | 112 mi | 4% | 5% |
| Kalawao County, HI | 147 mi | n/a | n/a |
| Honolulu County, HI | 217 mi | 12% | 4% |
| Kauai County, HI | 319 mi | 5% | 8% |
| San Francisco County, CA | 2315 mi | 0% | 3% |
| Marin County, CA | 2338 mi | 20% | 6% |
| San Mateo County, CA | 2340 mi | 10% | 3% |
| Sonoma County, CA | 2343 mi | 22% | 5% |
Sources: USDA SSURGO (September 9, 2025) · US Drought Monitor (November 3, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status