Island County Climate
Island County, Washington
Avg Annual Temp
51.2°F
Annual Precip
20.8"
Annual Snowfall
4.0"
Extreme Heat Days
0.3
days >= 90°F/yr
Monthly Temperature
Precipitation Calendar
Seasonal Overview
National Comparison
Climate Profile
About Island County Weather
Tempered by the Salish Sea
Island County’s 51.2°F average is tempered by the surrounding sea, keeping it cooler than the national median. It enjoys a mild maritime climate with moderate rainfall of 20.8 inches.
Island Rain Shadow Comfort
It is slightly warmer than the 49.9°F state average but much drier than the 38.5-inch state norm. Its location in the rain shadow of the Olympics provides a more Mediterranean feel.
Drier Than the Outer Coast
Island County is much drier than Grays Harbor, receiving only a fifth of the rainfall found on the outer coast. It also lacks the extreme heat seen in the eastern counties, recording zero days above 90°F.
Stable Temps and No Heat
The climate is remarkably stable, with summers averaging 60.4°F and winters averaging 42.2°F. Snowfall is minimal at 4.0 inches, and extreme heat is virtually non-existent.
Light Layers and Sea Breezes
Residents can skip the heavy-duty cooling systems since the county records no days over 90°F. Focus on wind-resistant apparel and light layers to manage the breezy, temperate coastal conditions.
Frequently Asked Questions
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Data source: NOAA National Centers for Environmental Information (NCEI), U.S. Climate Normals 1991-2020.
Climate normals are 30-year averages of weather variables computed from 1991 to 2020. Station data is aggregated to county level using spatial averaging. Data is informational only — not a substitute for official National Weather Service forecasts or emergency weather warnings.