The biggest allergy trigger during the fall months is ragweed. The weed typically begins releasing pollen with warm days and cool nights in August and can last into November.
“Warmth can extend the growing season for plants that produce ragweed pollen,” AccuWeather Meteorologist Ben Noll said. “Late-summer and early fall warmth has enhanced pollen levels across portions of the Plains, Midwest and Northeast.”
The Northeast, in particular, may have an extended season as dry conditions allow ragweed pollens to linger.
“Any pollen that’s in the air now is not going to get washed out,” AccuWeather Meteorologist Alan Reppert said.
Additionally, milder weather is forecast for the Northeast, mid-Atlantic and Southeast, so lower-than-usual chances for freezes could also help to extend the ragweed season.
“Meanwhile, some mid- and late-September cool snaps across the Plains and Midwest could result in a freeze, killing weeds and bringing an end to the ragweed season,” Noll said.
Though ragweed allergies typically calm down into late October with the arrival cooler air, allergy-aggravating mold spores can linger later into the season. Mold spores thrive on damp fall foliage.
Across the Plains, a wetter-than-normal fall could lead to increased levels of these allergens.
Enhanced levels of mold spores could also be an issue across the Southeast in the late fall as the second half of the season appears wetter than the first, Noll said.
Ultimately, however, experts say that the severity of a person’s fall allergies depends on their exposure to specific types of weed pollens, the amount of pollen in the air and their degree of hypersensitivity.
Despite these indicators, it’s difficult to predict how severe a season will ultimately become.
“This is because many factors play a role in influencing it, including things like temperature and precipitation levels,” Mauli Desai, MD, assistant professor of medicine in the Division of Clinical Immunology, Icahn School of Medicine at Mount Sinai, said.
“It is important for patients with fall allergies to be proactive, listen to pollen counts, talk to their doctor and prepare for a possible bad allergy season.”