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Hillsborough County, New Hampshire
A shallow water table limits basements on 28% of Hillsborough County's mapped land and the 8th highest of 10 New Hampshire counties. Shrink-swell clay limits houses without basements on 3%.
None of the county is in drought on the October 13, 2026 Drought Monitor map, after 3.7% a week earlier. FEMA's flood data list 38 flood losses here since 2016, 58% of them in buildings with basements. 53% of homes were built before 1980, against 50% nationally; the median home dates from 1978.
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 Hillsborough County
| Expansive clay (limits slab homes) | 2.6% |
| High water table (limits basements) | 28.1% |
| Septic fields very limited | 89.1% |
| Clay swell (LEP, by area) | 0.8% |
| High-swell land (LEP 6%+) | 2.6% |
| Urban land, not rated | 1.4% |
| Mapped soil | 570,253 acres |
| Soil series | Share here | Series nationally: high water table |
|---|---|---|
| Monadnock | 12% | n/a |
| Canton | 12% | n/a |
| Marlow | 11% | n/a |
| Hinckley | 5% | n/a |
| Windsor | 5% | n/a |
| Tunbridge | 4% | n/a |
How we count · survey areas NH601 (2025-09-09), NH602 (2025-09-09)
What the numbers mean here
On 28% of Hillsborough 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: 38.58 in, 9.15 in below the 1991-2020 average year of 47.73 in.
USDA rates 89% 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 51 of the last 52 weeks; the most was 100% of its area, in 9 weeks, most recently on the June 23, 2026 map.
| Category, October 13, 2026 | Share of county |
|---|---|
| D0 abnormally dry or worse | 48% |
| D1 moderate drought or worse | 0% |
| D2 severe or worse | 0% |
| D3 extreme or worse | 0% |
| D4 exceptional | 0% |
Flood losses since 2016
38 flood losses since 2016, $590,765 paid. The worst year was 2023, with 22. Foundations of the buildings, where recorded: 58% basements, 16% slabs, 26% elevated. Median water depth outside the building: 7 in.
| Year | Flood losses |
|---|---|
| 2016 | 1 |
| 2017 | 4 |
| 2018 | 7 |
| 2019 | 2 |
| 2020 | 0 |
| 2021 | 0 |
| 2022 | 1 |
| 2023 | 22 |
| 2024 | 1 |
| 2025 | 0 |
| 2026 to date | 0 |
Rain
| Average year, 1991-2020 | 47.73 in |
| 12 months to August 2026 | 38.58 in (-9.15) |
| 2025 | 41.63 in (-6.10) |
| Wettest year since 1895 | 2008: 62.10 in |
| Driest year since 1895 | 1965: 29.25 in |
| Days with 1 inch or more, normal at GREENVILLE 1 NNE (10 mi away) | 14.5 |
Homes
| Housing units | 177,734 |
| Median year built | 1978 |
| Built before 1980 | 53% |
| Built 2000 or later | 17% |
| Owner-occupied | 67% |
| Median value, owner-occupied | $421,100 |
| Single-family detached | 57% |
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 |
|---|---|---|---|
| Cheshire County, NH | 27 mi | 4% | 27% |
| Merrimack County, NH | 27 mi | 2% | 49% |
| Rockingham County, NH | 32 mi | under 1% | 48% |
| Middlesex County, MA | 34 mi | 0% | 41% |
| Sullivan County, NH | 40 mi | 2% | 26% |
| Worcester County, MA | 43 mi | under 1% | 51% |
| Strafford County, NH | 44 mi | 1% | 39% |
| Belknap County, NH | 45 mi | 2% | 42% |
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