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Puget Trough Climate

The Puget Trough’s climate is notorious for high rainfall and gray skies. It’s a temperate maritime climate, with mild, wet winters. Summers are warm and dry—if not particularly sunny. Mean January temperature is 39° F and mean July temperature is 65° F.

Precipitation, mostly falling as rain, averages 40 inches per year. The local average can vary greatly in the ecoregion, due to the prevailing moisture-laden winds from the southwest.

Rain shadow areas, affected by the high Olympic Mountains, include the northeast corner of the Olympic Peninsula, Whidbey Island, and the San Juan Islands. Average annual precipitation is 15 to 30 inches.

In Seattle or Tacoma, near sea level, average annual precipitation is 35 to 50 inches.

Where clouds slam into the Cascade Mountains, in the foothills, average annual precipitation is 60 to 80 inches.


For details of this ecoregion within Washington, click a subheading in the left column.

View the more general description of this ecoregion in North America

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