St. Johns County, Florida
A shallow water table limits basements on 88% of St. Johns County's mapped land, a higher share than 95% of US counties. Shrink-swell clay limits houses without basements on 5%.
None of the county is in drought on the October 13, 2026 Drought Monitor map, after 11.2% a week earlier. FEMA's flood data list 6,372 flood losses here since 2016, under 1% 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 St. Johns County
| Expansive clay (limits slab homes) | 5.1% |
| High water table (limits basements) | 88.3% |
| Septic fields very limited | 90.3% |
| Clay swell (LEP, by area) | 1.7% |
| High-swell land (LEP 6%+) | 5.4% |
| Mapped soil | 430,400 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Riviera | 10% | n/a |
| Myakka | 9% | 100% |
| Pomona | 7% | n/a |
| Holopaw | 6% | n/a |
| Immokalee | 5% | n/a |
| Tocoi | 4% | n/a |
How we count · survey areas FL109 (2025-08-28)
What the numbers mean here
On 88% of St. Johns 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: 36.54 in, 15.93 in below the 1991-2020 average year of 52.47 in.
USDA rates 90% 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 42 of the last 52 weeks; the most was 100% of its area, in 34 weeks, most recently on the September 29, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 11.3% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
6,372 flood losses since 2016, $244.4 million paid. The worst year was 2016, with 3,456. Foundations of the buildings, where recorded: under 1% basements, 63% slabs, 14% crawl spaces, 23% elevated. Median water depth outside the building: 16 in.
| Year | Flood losses |
|---|---|
| 2016 | 3,456 |
| 2017 | 1,723 |
| 2018 | 17 |
| 2019 | 20 |
| 2020 | 36 |
| 2021 | 18 |
| 2022 | 1,001 |
| 2023 | 20 |
| 2024 | 71 |
| 2025 | 8 |
| 2026 to date | 2 |
Rain
| Average year, 1991-2020 | 52.47 in |
| 12 months to August 2026 | 36.54 in (-15.93) |
| 2025 | 43.69 in (-8.78) |
| Wettest year since 1895 | 1964: 72.41 in |
| Driest year since 1895 | 1990: 32.50 in |
| Days with 1 inch or more, normal at ST AUGUSTINE LIGHTHOUSE (6 mi away) | 15.6 |
Homes
| Housing units | 133,504 |
| Median year built | 2004 |
| Built before 1980 | 14% |
| Built 2000 or later | 58% |
| Owner-occupied | 82% |
| Median value, owner-occupied | $489,200 |
| Single-family detached | 72% |
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 |
|---|---|---|---|
| Flagler County, FL | 29 mi | 6% | 93% |
| Clay County, FL | 30 mi | under 1% | 68% |
| Putnam County, FL | 31 mi | 1% | 68% |
| Duval County, FL | 35 mi | 6% | 78% |
| Bradford County, FL | 47 mi | 0% | 93% |
| Nassau County, FL | 55 mi | 7% | 93% |
| Volusia County, FL | 58 mi | 3% | 74% |
| Union County, FL | 60 mi | 0% | 94% |
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