allergies in september

​Late summer/early fall ragweed is the most common cause of fall allergies. Depending on where you live, ragweed-fueled fall allergies can start in August or September and continue through October and possibly November. Pollen grains are lightweight and spread easily, especially on windy days. The more wet and windy autumn is in your area, the more easily the pollen spreads, and the worse your symptoms will feel.