ZIP code · Potomac · Maryland · United States

ZIP code 20859 — Potomac

ZIP code 20859 serves Potomac, Maryland.

Postal code: 20859
Single source Value from one source, not cross-checked.
City: Potomac
County: Montgomery
State: Maryland
Country: United States
Coordinates: 39.1440, -77.2076 — precision precise (locality)
View on OpenStreetMap
USDA hardiness zone: 7b (5 to 10 °F)
Planting / growing zone from the 2023 USDA Plant Hardiness Zone Map: average annual extreme minimum temperature, 1991–2020.
Time zone: America/New_York (UTC−5 / UTC−4 DST)
Area codes: 301, 240, 227 (from the nearest rate centre)
Telephone area codes serving this ZIP (NANPA central-office assignments). A ZIP and an area code are different boundaries; at a border both codes may apply.

Tools: compare 20859 with another ZIP · ZIPs within 25 miles · distance from 20859

Climate — monthly normals

Warmest month Jul (avg high 87°F), coldest Jan (avg low 27°F).

	Jan	Feb	Mar	Apr	May	Jun	Jul	Aug	Sep	Oct	Nov	Dec
Avg high °F	42	45	54	66	74	82	87	85	78	66	56	46
Avg low °F	27	28	36	46	55	64	69	67	60	48	38	31
Precip in	3.1	2.6	3.7	3.2	3.5	4.0	4.0	3.0	4.0	3.5	3.3	3.4

NOAA 1991–2020 climate normals from the nearest station: ROCKVILLE 1 NE (4.3 mi) · NOAA NCEI

About this page

US ZIP codes have five digits. They are postal routing areas, not administrative boundaries: a ZIP can span more than one city or county, and the city shown is the primary USPS name for that code.

GeoNames · NOAA NCEI · usda-phzm. Data generated on 2026-08-21. Methodology · Report an error on this page