What is thunderstorm asthma?

For people with asthma or hay fever, especially those who experience wheezing or coughing with their hay fever, thunderstorm asthma can be sudden, serious and even life threatening.

During grass pollen season (1 October – 31 December) you may notice an increase in asthma and hay fever. Grass pollen season also brings the chance of thunderstorm asthma.

Thunderstorm asthma is thought to be triggered by a unique combination of high amounts of grass pollen in the air and a certain type of thunderstorm.

The symptoms of asthma, hay fever and COVID-19 can be similar, and it can be difficult to tell the difference between them.

If you are experiencing symptoms different to your usual asthma and hay fever symptoms, they have restarted after a period of absence or if you are unsure – get tested for COVID-19 and stay home until you get your results.

The epidemic thunderstorm asthma risk forecast will be issued throughout the grass pollen season from 1 October to 31 December.

You can access the risk forecast via the VicEmergency website or app, the Health.Vic website or the Melbourne Pollen website or app.

If you have further questions on thunderstorm asthma, please call the department’s Environmental Health Unit on 1300 761 874 or email

© State of Victoria, Department of Health.

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