Thunder Storm Asthma

Thunderstorm asthma is an uncommon phenomenon where a large number of people, many of whom have never had a previous asthma diagnosis or treatment, experience asthma over a short period of time. It is thought to be triggered by high grass pollen levels and a specific type of thunderstorm.


In Victoria, grass pollen season typically runs from October 1st to December 31st.  Most events occur in November.


People at high risk of thunderstorm asthma include people with:

  • current asthma
  • past history of asthma
  • undiagnosed asthma
  • hay fever
  • rye grass sensitisation


People at increased risk should:

  • be aware of and understand the thunderstorm asthma phenomena
  • avoid exposure to thunderstorms in October through December especially the wind gusts that immediately precede them; smoke from bushfires; dust storms and heavy rain storms and go indoors with windows and doors closed and air conditioner on recirculate if in use. If in a car they should have windows up and air conditioner on recirculate
  • have an asthma action plan and/or have practical knowledge of 4 step asthma first aid
  • have reliever medication appropriately available in grass pollen season and know how to use it correctly (ideally with as spacer).  Reliever medication can be bought over the counter without a prescription at pharmacies if required.
  • have suitable treatment of any coexisting allergic rhinitis
  • be aware of forecasts for thunderstorms and pollen counts / download the VicEmergency app.
  • if reliever medication is needed more than two times per week, attend for GP review