Pollen Count in Seattle, WA

Seattle's mild, maritime climate and abundant rainfall create a lush, green environment that supports a long and varied allergy season, generally stretching from late winter through early fall.

Tree pollen is the earliest and often most intense trigger, beginning as early as February with alder, followed by birch, cedar, maple, cottonwood, and the region's abundant Douglas fir and western red cedar, with peaks typically occurring from March through May. As tree pollen wanes, grass pollen takes over from late May into July, driven primarily by orchard grass, timothy, ryegrass, and Kentucky bluegrass, which thrive in the Puget Sound's moist conditions.

Late spring often brings an overlap between lingering tree pollen and emerging grasses, intensifying symptoms for many sufferers. Weed pollen becomes more prominent from August through October, with plantain, sorrel, lamb's quarters, and nettle leading the way; ragweed is less dominant here than in the Midwest but still contributes.

Beyond pollen, Seattle's damp climate fosters persistent indoor and outdoor mold, particularly in fall and winter, while dust mites flourish year-round in humid homes. Occasional wildfire smoke in late summer adds another irritant.

Overall, Seattle's allergy profile is defined by an extended, tree- and grass-heavy season compounded by moisture-driven mold exposure.