Pittsburgh, PA Pollen Levels Today

Pittsburgh sits in a humid continental climate within the Ohio River Valley, where rolling terrain, dense tree cover, and frequent temperature inversions combine to trap airborne allergens and create a long, intense pollen season.

Tree pollen typically kicks off in late March and peaks from April into early May, dominated by oak, maple, birch, sycamore, hickory, walnut, and ash, with cedar and elm contributing earlier in the season. As trees wind down in late May, grass pollen takes over and remains problematic through July, driven largely by timothy, orchard, Kentucky bluegrass, and ryegrass.

This tree-to-grass handoff often overlaps in May and early June, producing some of the highest symptom loads of the year. Weed pollen emerges in August and peaks in September, with ragweed as the primary culprit, joined by lamb's quarters, plantain, pigweed, and nettle until the first hard frost.

Beyond pollen, Pittsburgh's humidity, river valleys, and aging housing stock foster persistent mold (especially Alternaria and Cladosporium) and dust mite exposure, while the region's lingering industrial air quality and particulate pollution can worsen symptoms.

Overall, Pittsburgh's allergy profile is defined by a long, overlapping pollen calendar intensified by humidity, mold, and trapped valley air.