Chicago, IL Pollen Levels Today

Chicago's position along Lake Michigan and its humid continental climate create a prolonged and varied allergy season, with sufferers often contending with overlapping triggers from early spring through late fall.

Tree pollen kicks things off in March and typically peaks in April and May, driven by oak, maple, birch, elm, ash, cottonwood, and mulberry—species that thrive throughout the city's parks and neighborhoods. As tree counts taper, grass pollen takes over from late May through July, with Kentucky bluegrass, timothy, orchard grass, and ryegrass acting as the dominant offenders across the region's lawns and prairies.

The transition between late tree season and early grass season often produces a brief but intense overlap that can worsen symptoms in June.

Weed pollen dominates from August through the first hard frost in October, with ragweed as the primary culprit, supported by lamb's quarters, pigweed, and sagebrush.

Beyond pollen, Chicago's lake-influenced humidity fuels persistent outdoor and indoor mold, particularly in late summer and fall, while dense urban traffic and industrial activity contribute to elevated particulate pollution that can amplify respiratory irritation.

Overall, Chicago's allergy profile is defined by a long, multi-phase pollen calendar intensified by Midwestern humidity, lakefront mold, and urban air quality concerns.