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Ragweed pollen climbing, but lower than average

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As many allergy sufferers know too well, September is prime time for ragweed pollen. But, mercifully, this year’s levels are tracking below many recent years.

“We’re sort of below average this year,” says Susan Kosisky, chief of the U.S. Army Centralized Allergen Extract Lab. “[Recent weekly counts are] half of what the weekly average is.”


(Susan Kosisky)

Kosisky doesn’t have a bulletproof explanation for the depressed ragweed counts, but the past summer’s wetter than average weather may have lent a helping hand.

“Ragweed tends to like it sunny and dry,” Kosisky says. “Rainfall always has a negative influence on pollen levels.”

Natural year-to-year variations in pollen levels may also be playing a role. Some years just randomly unleash less of the sneeze-inducing grains into the air, Kosisky says, irrespective of the weather.


(Susan Kosisky)

Although this year’s counts are below average, numbers in recent days have still rated high and are trending up. For example, today’s ragweed count reached 27.48 grains per cubic meter of air. Anything over 10 is considered “high” locally.

“There’s still plenty out there,” Kosisky says.

Related: Tree pollen spikes to highest level since 2010 (from the spring)

Jason is the Washington Post’s weather editor and Capital Weather Gang's chief meteorologist. He earned a master's degree in atmospheric science, and spent 10 years as a climate change science analyst for the U.S. government. He holds the Digital Seal of Approval from the National Weather Association.
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