Green Bay, WI Pollen Levels Today

Green Bay, Wisconsin, sits along the humid continental climate zone where Lake Michigan's moisture, cold winters, and warm summers shape a distinct and often intense allergy season.

Spring tree pollen typically emerges in late March and peaks through April and May, driven by abundant birch, oak, maple, elm, box elder, ash, poplar, and cedar across the Fox River Valley and surrounding woodlands. As trees begin to wane in late May, grass pollen takes over, peaking from early June through July, with timothy, Kentucky bluegrass, orchard grass, and ryegrass dominating lawns, pastures, and rural fields throughout Brown County.

By August, weed pollen ramps up and continues through the first hard frost in October, with ragweed being the most significant offender, alongside lamb's quarters, pigweed, plantain, and sagebrush. Overlap between late-season grasses and early ragweed in August often intensifies symptoms for sensitive individuals.

Beyond pollen, Green Bay's humidity, proximity to the bay, and agricultural surroundings contribute to persistent outdoor mold spores—especially alternaria and cladosporium—peaking in late summer and fall, while damp basements and heavy snow seasons fuel year-round indoor dust mite and mold exposure.

Overall, Green Bay's allergy profile is defined by a robust tree-pollen spring, a grass-heavy early summer, and a ragweed- and mold-driven fall.