Lots of precipitation a. PFW year round b. windward slopes with moist mP air from Pacific c. especially high precip in mountain ranges with orographic influence. Olympic mountains wettest locale in continental U.S., over 200 inches of rain per year. Coastal areas lost most broadleaf trees as a legacy from Ice Ages. Now supports huge redwoods, Douglas-fir, hemlocks.
Mountainous areas are have cold winters, favor needleleaf trees.