Thunderstorm Asthma: The Surprising Truth about Rain, Thunderstorms and Asthma
By: Laura Jetter, ARNP | September 23, 2026
The Midwest if full of surprising weather. From days with gentle rain to pounding thunderstorms, the state of Iowa sees all kinds of weather. However, pollen can be dramatically affected by a light rain or a thunderstorm and this may have implications for your overall allergy and asthma symptom control.
According to the American Academy of Allergy, Asthma & Immunology (AAAAI), a gentle, steady rain can act as an environmental “scrubber,” pulling pollen out of the air. However, severe thunderstorms do the exact opposite due to a mechanical process called a pollen burst.
Here is what happens during a thunderstorm to cause a pollen burst effect.
Moisture Shock: Intact pollen grains are relatively large. Your nose and upper airway usually filter them out, keeping them from reaching your lungs. However, when high humidity and heavy rain hit, these pollen grains rapidly absorb moisture, swell, and burst.
The Shattering Effect: A single burst pollen grain shatters into hundreds of tiny submicron pollen fragments. These fragments are up to 100 times smaller than the original pollen grain.
Microscopic particles: Because these fragments are so microscopic, they stay suspended in the air for hours after the storm passes. When you go out side and inhale, the now tiny pollen pieces bypass your nasal passages completely, traveling deep into the lower lungs where they trigger intense asthma attacks and allergy symptoms.
Wind Amplification: Another fact to consider: Strong wind updrafts during a storm pull whole pollen grains into the clouds where they rupture, while violent downdrafts concentrate these highly allergenic fragments right at ground level. Therefore, the wind patterns also play a role in the amount of pollen burst and how those fragments become concentrated at the ground level where we breathe.
In the end, although a gentle rain may be good for allergies, heavy downpours and thunderstorms can actually worsen allergy and asthma symptoms through the pollen burst effect and wind downdrafts that concentrate the tiny pollen fragments at the ground level. This phenomenon is often referred to as “thunderstorm asthma”, given that the pollen burst process is known for triggering asthma attacks. As we can not control the weather, it is important that you have a plan for good allergy and asthma control at baseline. Don’t settle for the fact that your asthma always flares after a thunderstorm. If you are struggling with allergies or asthma, make an appointment with one of our nurse practitioners today to improve your asthma and allergy control. This will ensure that you can navigate all kinds of weather with confidence.
