Thunderstorms Linked to Surge in Asthma ER Visits

A recent study linked thunderstorms to a surge in asthma-related emergency department (ED) visits. Lead author Diala Merheb, MD, internal medicine resident at the University of Kansas Medical Center, presented this research in a poster called “Thunderstorm-Associated Increases in Asthma ED Visits in a Midwestern US City: A Five-Year Review” on November 6 at the 2025 American College of Allergy, Asthma, & Allergy (ACAAI) Annual Scientific Meeting in Orlando, Florida.

“These results confirm that thunderstorms can pose a serious health risk for people with asthma, even in the United States,” Merheb said in a statement. “Because storms are unpredictable, patients and healthcare providers should include storm-specific precautions in asthma action plans.”

“Thunderstorm asthma” is not a new discovery, with documentation of this environmental phenomenon internationally. However, limited studies examine the link between thunderstorms and asthma in areas of the United States with heavy pollen. The World Allergy Organization considers thunderstorms a risk factor for asthma attacks in patients suffering from pollen allergy,

Merheb and colleagues conducted a retrospective analysis to assess whether thunderstorms were associated with increased asthma-related ED visits in Wichita, Kansas, as well as the relationship between storm-day admissions and age, gender, zip code, and ED disposition. The team analyzed 4439 asthma-related ER visits across 3 Wichita hospitals from January 2020 to December 2024 and identified 38 thunderstorm days during this period using meteorological records.

The study revealed that 14% of all asthma-related ER visits (n = 627) occurred on the 38 storm days, representing only 2% of the calendar days in the study period. During thunderstorms, the average number of asthma visits was nearly 18 per day (17.9), compared with just 3 (3.09) on non-storm days (Mann-Whitney U = 41,787.5; P < 5.55 × 10?²²).

Older age was the only demographic factor associated with the increased risk of storm-related ER visits (P =.002). Gender, zip code, and admission or discharge status did not significantly affect the likelihood of visiting during a storm.

Investigators noted that a surge of asthma-related visits during storms puts a significant burden on emergency departments. Overcrowding in the emergency department harms the entire hospital, limiting resources and quality of care, as well as increasing mortality and morbidity. 2

Overcrowding not only impacts patient care but also places a financial burden on hospitals.2 A 2020 study estimated that nationwide emergency department visits cost approximately $76.3 billion in total.3

How Thunderstorms Trigger Asthma

The term “thunderstorm asthma” was first reported in the 1980s in England and Australia, and the phenomenon continues to occur today.4

After severe thunderstorms passed through Melbourne, Australia, in 2016, more than 9000 people sought urgent medical care for asthma. This overwhelmed medical facilities, and ≥ 8 people died.4

“Thunderstorm asthma” describes an asthma attack that starts or worsens after a thunderstorm. It can occur in anyone with asthma, but most often affects people with seasonal allergic rhinitis.

Although rain tends to lower pollen counts, thunderstorms can have the opposite effect due to their unique sequence of events. First, cold downdrafts concentrate air participates, such as pollen and mold. Then, air particles are swept into the clouds. A combination of clouds, wind, humidity, and lightning breaks up the particles to a size that can easily enter the nose, sinuses, and lungs. After that, wind gusts concentrate these small particles so large amounts can be inhaled.4

Another study reported that 65% of individuals with seasonal allergies reported experiencing thunderstorm asthma, and among them, nearly half sought emergency hospital treatment.4

Among individuals with seasonal allergies, risk factors for experiencing thunderstorm asthma include poorly controlled asthma symptoms, a low score on a rapid exhalation test, greater levels of ryegrass pollen-specific IgE, greater eosinophil levels, and greater levels of exhaled nitric oxide.

Patients at risk for thunderstorm asthma may benefit from regularly checking the weather forecast to ensure they are taking their asthma medications correctly, have rescue medication on hand, and can stay indoors until the storm passes.

“…it’s smart to think about thunderstorms the same way you prepare for high-pollen days or cold weather,” said investigator Selina Gierer, DO, in the statement.1 “Understanding triggers and having a clear plan can help avoid emergency room visits.”

References

1. Thunderstorms Linked to Surge in Asthma ER Visits, New Study Shows. Acaai.org. Published 2025. Accessed December 9, 2025. https://annualmeeting.acaai.org/2025/thunderstorms.cfm

2. Sartini M, Carbone A, Demartini A, et al. Overcrowding in Emergency Department: Causes, Consequences, and Solutions—A Narrative Review. Healthcare. 2022;10(9):1625. doi:https://doi.org/10.3390/healthcare10091625

3. Emergency Department Utilization (EDU) - NCQA. NCQA. Published April 16, 2025. https://www.ncqa.org/report-cards/health-plans/state-of-health-care-quality-report/emergency-department-utilization-edu/

4. Shmerling R. Thunderstorm asthma: Bad weather, allergies, and asthma attacks. Harvard Health. Published June 22, 2022. https://www.health.harvard.edu/blog/thunderstorm-asthma-bad-weather-allergies-and-asthma-attacks-202206222766