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Montgomery County, Pennsylvania
A shallow water table limits basements on 44% of Montgomery County's mapped land, a higher share than 61% of US counties. Shrink-swell clay limits houses without basements on under 1%.
None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 1,137 flood losses here since 2016, 50% of them in buildings with basements. 61% of homes were built before 1980, against 50% nationally; the median home dates from 1971.
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 Montgomery County
| Expansive clay (limits slab homes) | under 0.1% |
| High water table (limits basements) | 44.0% |
| Septic fields very limited | 73.4% |
| Clay swell (LEP, by area) | 1.9% |
| High-swell land (LEP 6%+) | under 0.1% |
| Urban land, not rated | 27.6% |
| Mapped soil | 311,795 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Readington | 9% | n/a |
| Penn | 9% | n/a |
| Reaville | 7% | n/a |
| Abbottstown | 4% | n/a |
| Croton | 4% | n/a |
| Lehigh | 3% | n/a |
How we count · survey areas PA091 (2025-09-04)
What the numbers mean here
On 44% of Montgomery 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: 37.95 in, 9.98 in below the 1991-2020 average year of 47.93 in.
USDA rates 73% 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 48 of the last 52 weeks; the most was 100% of its area, in 13 weeks, most recently on the July 7, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 9.4% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
1,137 flood losses since 2016, $67.9 million paid. The worst year was 2021, with 634. Foundations of the buildings, where recorded: 50% basements, 22% slabs, 3% crawl spaces, 25% elevated. Median water depth outside the building: 29.5 in.
| Year | Flood losses |
|---|---|
| 2016 | 7 |
| 2017 | 11 |
| 2018 | 66 |
| 2019 | 93 |
| 2020 | 258 |
| 2021 | 634 |
| 2022 | 6 |
| 2023 | 27 |
| 2024 | 18 |
| 2025 | 4 |
| 2026 to date | 13 |
Rain
| Average year, 1991-2020 | 47.93 in |
| 12 months to August 2026 | 37.95 in (-9.98) |
| 2025 | 38.83 in (-9.10) |
| Wettest year since 1895 | 2018: 69.33 in |
| Driest year since 1895 | 1930: 31.15 in |
| Days with 1 inch or more, normal at GRATERFORD 1 E (3 mi away) | 12.9 |
Homes
| Housing units | 350,351 |
| Median year built | 1971 |
| Built before 1980 | 61% |
| Built 2000 or later | 17% |
| Owner-occupied | 71% |
| Median value, owner-occupied | $436,700 |
| Single-family detached | 53% |
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 |
|---|---|---|---|
| Bucks County, PA | 16 mi | under 1% | 52% |
| Philadelphia County, PA | 19 mi | 0% | 5% |
| Delaware County, PA | 20 mi | under 1% | 22% |
| Chester County, PA | 26 mi | under 1% | 21% |
| Lehigh County, PA | 30 mi | 0% | 22% |
| Berks County, PA | 33 mi | 0% | 27% |
| Hunterdon County, NJ | 34 mi | 0% | 31% |
| Mercer County, NJ | 35 mi | 0% | 44% |
Sources: USDA SSURGO (September 4, 2025) · US Drought Monitor (October 13, 2026) · FEMA NFIP v3 (September 9, 2026) · NOAA (August 2026) · Census ACS 2020-2024. Methods · Data status