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Mercer Island, WA Marine Weather Forecast

Overnight - 35°F
Dec 27, 2025
3 mph NNW
Partly Cloudy
Partly cloudy. Low around 35, with temperatures rising to around 37 overnight. North northwest wind around 3 mph.
Saturday - 43°F
Dec 27, 2025
1 to 5 mph NNE
Mostly Sunny
Mostly sunny, with a high near 43. North northeast wind 1 to 5 mph.
Saturday Night - 35°F
Dec 27, 2025
1 mph ESE
Mostly Cloudy
Mostly cloudy, with a low around 35. East southeast wind around 1 mph.
Sunday - 44°F
Dec 28, 2025
2 mph SE
Partly Sunny
Partly sunny, with a high near 44. Southeast wind around 2 mph.
Sunday Night - 36°F
Dec 28, 2025
2 mph ENE
Mostly Cloudy
Mostly cloudy, with a low around 36. East northeast wind around 2 mph.
Monday - 46°F
Dec 29, 2025
3 mph NNE
Mostly Cloudy
Mostly cloudy, with a high near 46.
Monday Night - 36°F
Dec 29, 2025
3 mph NNE
Mostly Cloudy
Mostly cloudy, with a low around 36.
Tuesday - 45°F
Dec 30, 2025
2 mph NE
Mostly Cloudy
Mostly cloudy, with a high near 45.
Tuesday Night - 39°F
Dec 30, 2025
2 mph SE
Mostly Cloudy
Mostly cloudy, with a low around 39.
Wednesday - 47°F
Dec 31, 2025
3 mph SSE
Slight Chance Light Rain
A slight chance of rain after 10am. Mostly cloudy, with a high near 47.
Wednesday Night - 41°F
Dec 31, 2025
3 mph SSE
Chance Light Rain
A chance of rain. Mostly cloudy, with a low around 41.
New Year's Day - 48°F
Jan 01, 2026
6 mph SSE
Light Rain Likely
Rain likely. Cloudy, with a high near 48.
Thursday Night - 42°F
Jan 01, 2026
7 mph S
Light Rain Likely
Rain likely. Mostly cloudy, with a low around 42.
Friday - 47°F
Jan 02, 2026
7 mph S
Light Rain Likely
Rain likely. Mostly cloudy, with a high near 47.

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