Pollen Count & Forecast for Seattle

Seattle’s tree pollen season (February-June) is dominated by Red Alder (Alnus rubra) and Birch (Betula); Alder is common in Discovery Park and along the Burke-Gilman Trail. Bigleaf Maple (Acer macrophyllum) and Western Red Cedar (Thuja plicata) are found in the Washington Park Arboretum. Summer (May-August) has high Grass (Poaceae) pollen levels, originating from the meadows at Magnuson Park and Green Lake.

Hilly terrain and Puget Sound breezes trap pollen in residential valleys. Autumn and winter see elevated Mould (Alternaria, Cladosporium) spore counts; spores are frequent in the moist soils of Seward Park and Ravenna Ravine. Decaying organic matter in forested areas increases counts during the wet season.