ZIP code · Mercer Island · Washington · United States
ZIP code 98040 — Mercer Island
ZIP code 98040 serves Mercer Island, Washington.
- Postal code
- 98040Single source Value from one source, not cross-checked.
- City
- Mercer Island
- County
- King FIPS 53033
- State
- Washington
- Country
- United States
- Coordinates
- 47.5603, -122.2281 — precision precise (locality)
View on OpenStreetMap - Population
- 25,282 (ZCTA, ACS 5-year)
- Population density
- 3,961 / sq mi
- Land area
- 6.4 sq mi (16.5 km²) (ZCTA, ACS 5-year)
- Median household income
- $202,359
- Per-capita income
- $120,120
- Median age
- 45.8
- Households
- 9,893
- Housing units
- 10,454
- Median home value
- $1,884,200
- Median gross rent
- $2,464 / month
- Congressional district
- WA-9 (119th Congress)
- USDA hardiness zone
- 9a (20 to 25 °F)Planting / growing zone from the 2023 USDA Plant Hardiness Zone Map: average annual extreme minimum temperature, 1991–2020.
- Time zone
- America/Los_Angeles (UTC−8 / UTC−7 DST)
- Area code
- 425 (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 98040 with another ZIP · ZIPs within 25 miles · distance from 98040
Map of ZIP code 98040
Climate — monthly normals
Warmest month Aug (avg high 77°F), coldest Dec (avg low 36°F).
| Jan | Feb | Mar | Apr | May | Jun | Jul | Aug | Sep | Oct | Nov | Dec | |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Avg high °F | 49 | 51 | 55 | 60 | 67 | 71 | 77 | 77 | 72 | 61 | 53 | 48 |
| Avg low °F | 37 | 37 | 39 | 44 | 49 | 54 | 58 | 58 | 54 | 46 | 40 | 36 |
| Precip in | 5.2 | 3.7 | 3.9 | 2.9 | 2.0 | 1.2 | 0.6 | 0.8 | 1.4 | 3.5 | 5.8 | 5.5 |
NOAA 1991–2020 climate normals from the nearest station: SEATTLE BOEING FLD (4.0 mi) · NOAA NCEI
Places in ZIP 98040
- 19 schools
- 1 hospitals & clinics
- 1 doctors & dentists
- 2 pharmacies
- 3 supermarkets
- 28 restaurants & cafés
- 1 bars & pubs
- 38 parks
- 27 playgrounds
- 15 gyms & sports centres
- 1 libraries
- 2 post offices
- 11 places of worship
- 8 banks
- 2 gas stations
- 2 EV charging stations
- 2 police & fire stations
Places mapped inside this ZIP’s ZCTA area in OpenStreetMap. OSM is community-maintained: counts reflect what has been mapped, and completeness varies by area — treat them as at-least figures. © OpenStreetMap contributors (ODbL) · Methodology
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 · U.S. Census Bureau (ACS) · U.S. Census Bureau · NOAA NCEI · usda-phzm. Data generated on 2026-08-21. Methodology · Report an error on this page