Grass pollen season, which typically runs from the start of October until the end of December, brings with it a seasonal increase in asthma and hay fever and the chance of thunderstorm asthma.

What is thunderstorm asthma?

Thunderstorm asthma is asthma that is triggered by a particular type of thunderstorm when there is a high amount of grass pollen in the air (typically between October and end December).

It can result in people wheezing, feeling short of breath, and tight in the chest with coughing.

This can be sudden, serious, and even life threatening.

When large numbers of people develop asthma symptoms over a short period of time, caused by high amounts of grass pollen and a certain type of thunderstorm, it is known as epidemic thunderstorm asthma.

For more information on thunderstorm asthma visit

Being prepared

On high-risk thunderstorm asthma risk forecast days, people with asthma or spring hay fever can reduce their risk by avoiding the storms. On these days, at-risk people should go inside, close windows and turn off any air conditioners that bring air and possible pollen fragments in from outside.

Those at risk should check the epidemic thunderstorm asthma risk forecast daily at (External link) or download the app and set up a watch zone.

Victoria's forecasting system, which will operate until 31 December, forecasts three days in advance and provides a low (green), moderate (orange) or high (red) risk forecast across the nine Victorian weather districts.

Who is at risk?

You are at risk of thunderstorm asthma if you:

  • have asthma (or have had asthma in the past)

  • have hay fever (allergy affecting the nose) during Spring.

If you feel short of breath, tight in the chest, wheeze or cough during pollen season – you might have undiagnosed asthma.