The three pollen seasons
- Trees: tree pollination begins earliest in the year, so spring allergies can start as early as February.
- Grasses: grass pollen follows later in the spring and into summer.
- Ragweed and other weeds: ragweed releases pollen from August to November. See ragweed season.
- Mold: molds grow quickly in heat and high humidity, and a rainy spring can raise mold levels.
When to start allergy medicine
Allergists recommend starting medicine about two weeks before your symptoms usually begin if you have a history of seasonal allergies (ACAAI). For tree pollen, that can mean late January or February in many places. Compare options on their labels: how to choose an allergy medicine, non-drowsy options and allergy medicine for kids.
What time of day pollen is highest
- In tree and grass season (spring and summer), pollen levels are highest in the evening.
- In ragweed season (late summer and fall), levels are highest in the morning.
Plan outdoor exercise and yard work for the lower times, and keep windows and doors shut at home and in the car during your season.
Where allergies are worst
The Asthma and Allergy Foundation of America ranks the 100 largest U.S. metro areas each year. In 2026, Boise, San Diego and Tulsa topped the list. See the worst cities for allergies.
Sources
Not medical advice. If you have asthma or symptoms that over-the-counter medicine does not control, see a doctor or an allergist.
