Ohio Allergy Season Guide

Ohio experiences a humid continental climate with hot, humid summers and cold, snowy winters.

Maple, birch, oak, and ash drive the spring tree season. Grass pollen peaks in late May and June, and ragweed dominates from mid-August through the first hard frost.

Heavy leaf litter, agricultural activity, and humid summers produce very high outdoor mold counts from late summer through fall.

Allergy patterns vary by elevation and proximity to coast or mountains within Ohio, but most of the state shares a common seasonal rhythm of spring tree pollen, summer grass pollen, and late-summer to fall weed pollen.