Thunderstorms Triggering Surge in ER Visits for Asthma Attacks

When thunderstorms roll across Kansas, it’s not just heavy rain and lightning that pose a threat. A new study finds that thunderstorms can trigger a surge in ER visits for asthma attacks.

Researchers at University of Kansas Medical Center analyzed more than 4,400 asthma-related ER visits to three Wichita hospitals from 2020 through 2024. Using weather records from the National Centers for Environmental Information, they identified 38 heavy thunderstorm days over the five-year period.

Thunderstorm days accounted for only about 2 percent of the calendar days. Yet, 14 percent of all asthma-related ER visits occurred on those days. Hospitals averaged 18 asthma-related visits on thunderstorm days, compared with three on non-stormy days. That’s a fivefold increase.

“These results confirm that thunderstorms can pose a serious health risk for people with asthma,” says Dr. Diala Merheb, lead author of the study. Merheb is an internal medicine resident at University of Kansas Medical Center in Wichita.

Thunderstorm Events

“Thunderstorm asthma,” as it’s called, was first documented in England in the 1980s. The most catastrophic thunderstorm asthma incident to date occurred in 2016 in Melbourne, Australia.

After thunderstorms swept through the region, nearly 3,400 people more than the expected level went to emergency departments for asthma attacks. Thirty-five were admitted to intensive care, and 10 died.

Emergency services, facing calls 147 percent above normal, were overwhelmed. The Emergency Services Telecommunications Authority fielded more than 2,300 calls, an “unprecedented level of demand.”

The Kansas study is among the first to report the phenomenon in the United States, although previous studies in Minneapolis–St. Paul and Louisiana have also documented it, Merheb says.

How Do Storms Set Off Asthma?

What unleashes thunderstorm asthma? It’s thought that pollen granules, swept into the sky by storm winds, rupture in the high humidity and disperse allergens into the air below.

Typically, rainfall helps relieve allergies by washing away airborne pollen. But a thunderstorm can be more intense. It can lift pollen into the clouds, where the high humidity causes grains to burst. Powerful downdrafts can then spread the fragments.

“Weather changes such as shifts in wind, humidity, and pollen fragmentation may increase the concentration of allergen particles in the air,” Merheb says.

Down below, people inhale these tiny fragments deep into their lungs. One theory is the fragments cause more inflammation in the lungs than typical, intact pollen. Another is that outdoor molds, which also send out their spores in the spring and summer when thunderstorms occur, contribute to the asthma exacerbations.

Together, these can trigger asthma attacks in people with sensitive airways. During the Melbourne incident, grass pollen counts were extremely high at the time of the storm.

The Kansas study didn’t measure pollen counts, but Merheb says this is planned for future research.

To be sure, large-scale outbreaks like the 2016 Melbourne event remain rare. But “smaller increases in asthma activity may happen more often and go unnoticed,” Merhab says. “Several U.S. studies have shown similar trends, suggesting this may be a recurring but underrecognized pattern.”

The World Allergy Organization considers thunderstorms a risk factor for asthma attacks in patients with pollen allergy.

How To Prepare

Merheb advises people with asthma to be proactive when storms are forecasted. Take asthma controller medications such as inhaled corticosteroids, and have rescue inhalers on hand. Also be sure to have an asthma action plan in place.

The Kansas study found older people in the region were at higher risk of an asthma-related emergency department on stormy days than younger people. But the study on the Australian incident found younger men of Asian or Indian ethnicity were hit hard. As well, 28 percent of those hospitalized had never been diagnosed with asthma.

“Avoiding outdoor exposure during thunderstorm events, keeping windows closed, and maintaining regular use of prescribed medications can all make a difference,” Merheb says.

The research was presented at the 2025 American College of Allergy, Asthma & Immunology (ACAAI) Annual Scientific Meeting in Orlando in November 2025.