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Sullivan County, New Hampshire

A shallow water table limits basements on 26% of Sullivan County's mapped land and the 10th highest of 10 New Hampshire counties. Shrink-swell clay limits houses without basements on 2%.

None of the county is in drought on the October 13, 2026 Drought Monitor map. FEMA's flood data list 18 flood losses here since 2016. 61% of homes were built before 1980, against 50% nationally; the median home dates from 1974.

Data as of October 13, 2026 · sources

2%

expansive clay: shrink-swell limits slab homes

26%

high water table: limits basements

0%

in drought, October 13, 2026

61%

of homes built before 1980

Soil under Sullivan County

Expansive clay (limits slab homes)1.7%
High water table (limits basements)25.8%
Septic fields very limited83.4%
Clay swell (LEP, by area)1.0%
High-swell land (LEP 6%+)1.7%
Mapped soil353,305 acres
Soil seriesShare hereSeries nationally: high water table
Monadnock19%n/a
Marlow12%n/a
Lyman7%n/a
Peru6%n/a
Hermon6%n/a
Bernardston4%n/a
Windsor County: 27%Merrimack County: 49%Cheshire County: 27%Windham County: 29%Hillsborough County: 28%Belknap County: 42%Grafton County: 29%Orange County: 36%Sullivan County WindsorMerrimackCheshireWindhamHillsboroughBelknapGraftonOrangeSullivan
Sullivan County (heavy outline) and nearby counties, shaded by high water table share.under 10%10-25%25-40%40-60%60%+

How we count · survey areas NH019 (2025-09-09)

What the numbers mean here

On 26% of Sullivan 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: 39.31 in, 6.57 in below the 1991-2020 average year of 45.88 in.

USDA rates 83% 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 38 of the last 52 weeks; the most was 100% of its area, in 7 weeks, most recently on the May 12, 2026 map.

October 21, 2025Share of area in drought, weeklyOctober 13, 2026
Category, October 13, 2026Share of county
D0 abnormally dry or worse100%
D1 moderate drought or worse0%
D2 severe or worse0%
D3 extreme or worse0%
D4 exceptional0%

Flood losses since 2016

18 flood losses since 2016, $903,672 paid. The worst year was 2023, with 13.

YearFlood losses
20160
20170
20181
20191
20200
20213
20220
202313
20240
20250
2026 to date0

Rain

Average year, 1991-202045.88 in
12 months to August 202639.31 in (-6.57)
202538.89 in (-6.99)
Wettest year since 18952005: 59.95 in
Driest year since 18951965: 29.82 in
Days with 1 inch or more, normal at NEWPORT (2 mi away)9.3

Homes

Housing units21,958
Median year built1974
Built before 198061%
Built 2000 or later14%
Owner-occupied75%
Median value, owner-occupied$268,700
Single-family detached74%

What repairs cost

Published ranges from cost guides, not quotes. More sources, and where they disagree.

WorkRangeSource
Basement waterproofing, US $3,000 to $10,000 Fixr, February 6, 2026
Sump pump installation, US $800 to $2,000 Fixr, January 31, 2025
Crawl space encapsulation, US $2,000 to $8,000 Fixr, August 29, 2025

Nearby counties

PlaceDistanceExpansive clayHigh water table
Windsor County, VT 24 mi 0% 27%
Merrimack County, NH 28 mi 2% 49%
Cheshire County, NH 30 mi 4% 27%
Windham County, VT 36 mi 0% 29%
Hillsborough County, NH 40 mi 3% 28%
Belknap County, NH 41 mi 2% 42%
Grafton County, NH 43 mi 1% 29%
Orange County, VT 45 mi 0% 36%

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