Storms Don’t Wash Pollen Away—They Burst It Into Tiny Pieces. Here's How It Can Lead To "Thunderstorm Asthma."

— By Megan Wollerton | April 22, 2026

A rural road in Kansas leads toward a storm. Thunderstorms make pollen worse as high humidity, wind, and lightning break pollen grains into hundreds of tiny, allergen-packed fragments. These small particles penetrate deeper into the lungs than normal sized pollen, triggering severe allergic reactions and asthma attacks. Jim Reed, National Geographic Image Collection

Climatologist Corey Davis knows what it’s like to live with allergies. “I wake up every morning and I'm all stopped up. I feel like I've got a cold, and then I remember, no, it's just the spring,” says Davis, who works at the North Carolina State Climate Office.

Pollen is a major culprit. Over 80 million people in the United States suffer from pollen-induced seasonal allergies. And not only is the pollen season getting longer, the pollen count—how many of those allergy-inducing fragments are floating around in the air at any given time—is going up. With warming temperatures, pollen's presence in our lives will probably keep getting worse.

But a springtime weather pattern may be fueling this phenomenon. Thunderstorms that create high winds, intense rain, big temperature shifts, and hail, can explode those individual pollen particles into even tinier pieces. These severe storms are more likely to occur as global temperatures continue to rise. And they happen frequently in the midwestern U.S. during the spring when allergens are at their peak.

Here’s more on what happens to pollen during storms, how it can lead to “thunderstorm asthma,” and what we can do to prepare for longer and more intense allergy seasons ahead.

What Happens To Pollen During a Storm?

Spring thunderstorms aren’t a new phenomenon, but warming temperatures increase their likelihood and severity. Increased humidity, intensifying rain, and stronger winds give pollen even more opportunity to spread and break into tiny pieces.

Thunderstorm winds hurl debris all over the place, explains West Virginia's WCHS meteorologist Dante Ricci. “Any pollen, any dust, anything that is sitting on the ground, will be dispersed, and it will be blown onto cars, into the circulating air, perhaps into homes, if the windows are open, and onto anyone who is outside and unfortunate to be in the path.”

But the most significant effect of these intense winds, along with soaring humidity and rain, is that they cause individual grains of pollen to burst into even smaller bits, called sub-pollen.

While the rain does wash some of the pollen away, those tiny burst particles can remain in the air for hours after a storm. And that spring rain can also cause even more plants to produce allergens.

“The particle size matters a lot,” says University of Utah School of Biological Sciences professor William Anderegg. “A lot of pollen is 10 microns or bigger, and that's less damaging to your lungs than when it gets broken up into smaller pieces." When the pollen gets to 2.5 microns or smaller, it becomes a bigger health concern.

What Sub-Pollen Does To The Body

Regular pollen grains are too big to get all the way into the lungs, says pediatric pulmonologist Erica Stevens. These grains tend to cause standard hay fever symptoms, like congestion and an irritated throat and eyes, she explains.

When storms burst the allergens into hundreds of tiny pieces, though, “folks are at major risk of severe asthma attacks,” Stevens says—including a potentially serious medical emergency known as thunderstorm asthma.

“The body has an overreaction to it, and the lungs create a ton of additional mucus that can be very difficult to cough up,” she says.

This can lead to bronchospasm, or a tightening of the muscles around the airway. Bronchospasm makes it hard to breathe and can lead to respiratory failure in very serious cases, Stevens says. Asthma can cause bronchospasm, but so can other things, like an allergic reaction or lung disease.

The worst reported instance of thunderstorm asthma occurred in November 2016 in Melbourne, Australia. Over 3,400 people experiencing asthma symptoms flooded emergency rooms and 10 people died. Cases of thunderstorm asthma have also been reported in Asia, Italy, the Middle East, North America, and the United Kingdom.

What To Do As Pollen Season Intensifies

Stevens suggests keeping an eye on the weather apps, so you know the air quality and pollen count on any given day. AccuWeather lists the daily severity of common allergies, like tree pollen, ragweed pollen, mold, grass pollen, and dust and dander from low to extreme.

Pollen is usually at its most intense from around sunrise to early afternoon, says Ricci. Try to plan your outings for later in the evening and run your air conditioner to help filter irritants like pollen and dust out of your home.

If you already deal with allergies and asthma, keep up with your regular medications and always have your “rescue inhaler” or other needed medications on hand, says Stevens.

“Biologic injectable medications” have also advanced how allergies and asthma are treated and help reduce the chances of a severe allergic response in a lot of people, Stevens says. Different from regular allergy shots, biologic injectables use living cells to help stop the immune system from reacting to allergens.