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Montgomery County, Maryland

A shallow water table limits basements on 19% of Montgomery County's mapped land. Shrink-swell clay limits houses without basements on 1%.

2.1% of the county is in drought on the October 13, 2026 Drought Monitor map, down from 3.9% a week earlier. FEMA's flood data list 234 flood losses here since 2016, 75% of them in buildings with basements. 49% of homes were built before 1980, against 50% nationally; the median home dates from 1980.

Data as of October 13, 2026 · sources

1%

expansive clay: shrink-swell limits slab homes

19%

high water table: limits basements

2%

in drought, October 13, 2026

49%

of homes built before 1980

Soil under Montgomery County

Expansive clay (limits slab homes)0.5%
High water table (limits basements)18.7%
Septic fields very limited82.6%
Clay swell (LEP, by area)2.1%
High-swell land (LEP 6%+)1.0%
Urban land, not rated4.8%
Mapped soil325,241 acres
Soil seriesShare hereSeries nationally: high water table
Glenelg20%0%
Gaila10%n/a
Blocktown9%n/a
Brinklow7%n/a
Penn5%n/a
Occoquan4%n/a
Howard County: 24%Falls Church city: 13%Arlington County: 3%District of Columbia: 9%Fairfax city: 10%Fairfax County: 33%Alexandria city: 44%Loudoun County: 31%Montgomery County HowardFalls Church cityArlingtonDistrict of ColumbiaFairfax cityFairfaxAlexandria cityLoudounMontgomery
Montgomery 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 MD031 (2025-09-09)

What the numbers mean here

On 19% 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: 32.73 in, 11.83 in below the 1991-2020 average year of 44.56 in.

USDA rates 83% of the land very limited for septic absorption fields.

Drought

2.1% of the county is in drought (D1 or worse) on the October 13, 2026 map. Part of the county was in drought in 52 of the last 52 weeks; the most was 100% of its area, in 31 weeks, most recently on the July 28, 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 worse2.1%
D2 severe or worse0%
D3 extreme or worse0%
D4 exceptional0%

Flood losses since 2016

234 flood losses since 2016, $1.9 million paid. The worst year was 2020, with 43. Foundations of the buildings, where recorded: 75% basements, 6% slabs, 2% crawl spaces, 17% elevated. Median water depth outside the building: 7 in.

YearFlood losses
201629
201717
201832
201933
202043
202133
20228
20239
20248
202521
2026 to date1

Rain

Average year, 1991-202044.56 in
12 months to August 202632.73 in (-11.83)
202533.76 in (-10.80)
Wettest year since 18952018: 64.25 in
Driest year since 18951930: 20.28 in
Days with 1 inch or more, normal at DAMASCUS 3 SSW (9 mi away)13.3

Homes

Housing units406,531
Median year built1980
Built before 198049%
Built 2000 or later21%
Owner-occupied65%
Median value, owner-occupied$640,300
Single-family detached47%

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
Howard County, MD 17 mi 1% 24%
Falls Church city, VA 18 mi 0% 13%
Arlington County, VA 19 mi 0% 3%
District of Columbia, DC 19 mi 0% 9%
Fairfax city, VA 20 mi 2% 10%
Fairfax County, VA 22 mi 6% 33%
Alexandria city, VA 23 mi 3% 44%
Loudoun County, VA 24 mi 8% 31%

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