Cincinnati, OH Pollen Levels Today

Cincinnati sits in the Ohio River Valley, a geographic bowl where humid continental weather and river-basin air stagnation combine to trap pollen and mold spores, giving the city a consistently high ranking among the nation's most challenging allergy locations.

Tree pollen launches the season in March and peaks in April and early May, driven by oak, maple, sycamore, birch, cedar, ash, and the region's abundant hickory and walnut stands. As trees taper off in late May, grass pollen takes over through June and into July, with timothy, orchard, Kentucky bluegrass, and fescue dominating the landscape and often overlapping with lingering tree release to intensify early-summer symptoms.

Weed season arrives in mid-August and runs through the first hard frost in October, led by ragweed — which thrives along the Ohio River floodplains — alongside lamb's quarters, pigweed, plantain, and nettle.

Beyond pollen, Cincinnati's humidity and frequent rainfall fuel year-round outdoor mold (especially Alternaria and Cladosporium) that spikes in late summer and fall, while valley-trapped ozone, particulate pollution, and indoor dust mites add to the burden.

Overall, Cincinnati's allergy profile is defined by a long, overlapping pollen calendar amplified by valley geography, persistent humidity, and elevated mold and air-quality pressures.