Illinois pollen and allergy seasons
Illinois has a spring tree season and one of the heavier ragweed seasons in the country in late summer.
Twelve month pollen calendar
What is active in August
Cities in Illinois
No tracked cities yet for Illinois.
Today and worst today come from live readings where available. Typical shows the usual level for this month from the seasonal profile.
Pollen is only half of what's in the air. See today's air quality in Illinois for ozone, dust, and smoke readings by city.
The Illinois allergy season
Allergy levels in Illinois peak in September, when ragweed pollen runs highest. The season moves through tree pollen around April, grass in June, weed pollen such as ragweed in September. Levels start to climb around March. The lowest pollen levels of the year arrive in January.
Common questions
When does allergy season start in Illinois?
Pollen levels in Illinois usually begin climbing in March and reach their highest point in September.
What is the worst month for allergies in Illinois?
September is typically the worst month in Illinois, driven by ragweed pollen.
When does ragweed season end in Illinois?
Ragweed pollen in Illinois usually fades by the end of October, after the first hard frost in colder areas.
When is the best time for allergies in Illinois?
January usually brings the lowest pollen levels of the year in Illinois.