Mercer Island, WA Weather & Growing Conditions
Today
81°F
Sunny then Areas Of Smoke
Areas of smoke after noon. Sunny, with a high near 81. North wind 5 to 8 mph.
7-day forecast
| When | Temp | Forecast | Wind | Precip |
|---|---|---|---|---|
| Today | 81°F | Sunny then Areas Of Smoke | 5 to 8 mph N | 0% |
| Tonight | 60°F | Areas Of Smoke | 3 to 8 mph NNE | 0% |
| Wednesday | 86°F | Patchy Smoke | 3 to 7 mph N | 0% |
| Wednesday Night | 62°F | Mostly Clear | 1 to 7 mph NNE | 0% |
| Thursday | 86°F | Sunny | 1 to 6 mph NW | 0% |
| Thursday Night | 63°F | Mostly Clear | 2 to 6 mph W | 0% |
| Friday | 87°F | Sunny | 5 mph SW | 0% |
| Friday Night | 62°F | Mostly Clear | 1 to 6 mph NNE | 0% |
| Saturday | 84°F | Sunny | 1 to 6 mph WNW | 0% |
| Saturday Night | 60°F | Mostly Clear | 2 to 8 mph NNE | 1% |
| Sunday | 79°F | Mostly Sunny | 3 mph WSW | 1% |
| Sunday Night | 59°F | Mostly Clear | 3 mph NNE | 1% |
| Monday | 78°F | Mostly Sunny | 5 mph WNW | 1% |
| Monday Night | 59°F | Partly Cloudy | 5 mph NNE | 0% |
Forecast source: National Weather Service (api.weather.gov). Updated through the day.
Growing snapshot for Mercer Island, WA
Last spring frost
Mar 13
First fall frost
Nov 17
Growing season
247 days
Hardiness zone
9a
Explore more for Mercer Island, WA: full frost dates · planting calendar · Washington frost dates
Climate data from the nearest NOAA station, Seattle Boeing Fld, Wa (4 mi). Frost dates are 1991–2020 averages, not a forecast. Page updated Aug 4, 2026.