Seasonal sneezing is back: Once the weather turns slightly cooler at the end of summer, allergic rhinitis, or nasal allergies, appear in full force.

In the fall, the culprit is typically ragweed, which grows across much of the country, producing as many as one billion pollen grains per plant. As winter nears and we head indoors for the year, mold can cause fall allergies, too.

If this year’s season feels worse than usual, it could be more than your imagination. Across the country, allergies are becoming more severe.

Read More: http://www.weather.com/health/allergy/news/worst-fall-allergy-cities-2015