Louisville, KY Pollen Levels Today

Louisville, Kentucky consistently ranks among the most challenging U.S. cities for seasonal allergies, a reputation driven by its location in the Ohio River Valley, where humid summers, mild winters, and stagnant air trap pollen and mold spores close to the ground.

Tree pollen kicks off the allergy calendar in late February and peaks from March through May, with oak, maple, sycamore, cedar, birch, hickory, and ash among the dominant contributors across the region's dense hardwood canopy.

As tree season winds down, grass pollen takes over from May into July, led by Kentucky bluegrass, timothy, orchard grass, and Bermuda, often overlapping with lingering tree pollen in late spring to intensify symptoms.

Weed season follows in August and runs through the first hard frost, typically in late October, with ragweed as the primary offender alongside lamb's quarters, pigweed, plantain, and sagebrush.

Beyond pollen, Louisville's high humidity fuels year-round mold growth—both outdoor spores like alternaria and cladosporium and indoor mold—while dust mites, urban air pollution, and ozone from river valley inversions add further irritation.

Overall, Louisville's allergy profile is defined by a long, overlapping pollen calendar amplified by persistent humidity, heavy tree cover, and geography that keeps allergens concentrated.