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Asthma and thunderstorms

What is the link between hay fever, thunderstorms and asthma?

Who is at risk of thunderstorm asthma?

Could I have undiagnosed asthma?

How can I prepare for thunderstorm asthma? 

What should I do if a thunderstorm is forecast in pollen season?

How do I stay informed about weather and pollen counts?

How do I stay informed about asthma?

  • Thunderstorm asthma is a form of asthma that is triggered by an uncommon combination of high pollen (usually during late Spring to early Summer) and a certain kind of thunderstorm.
  • Anyone can be affected, even if you don’t have a history of asthma.
  • People at increased risk have a history of asthma, have unrecognised asthma, have hay fever (allergic rhinitis), particularly seasonal hay fever, or are allergic to grass pollen.
  • People experiencing asthma symptoms even if for the first time should not  ignore it, and should seek medical advice as soon as possible.
  • An asthma flare up can vary in severity and can be life threatening. If there are signs that a person’s condition is deteriorating, urgent care should be sought. Call Triple Zero (000).
  • Be aware of forecast thunderstorms in the pollen season particularly on days with a HIGH or EXTREME pollen count.
  • Where possible, stay indoors with doors and windows closed until the storm front has passed.

What is the link between hay fever, thunderstorms and asthma?

Most people are familiar with seasonal hay fever, which in Australia is most commonly due to grass pollens. This pollen is relatively large and the grains are caught in people’s upper airways resulting in a runny nose, itchy throat, watery eyes and sneezing. These pollen grains are generally too large to travel into the lower parts of the lungs.

The grass pollen season in Australia varies depending on where you live. In Melbourne, this is usually between 1 October and 31 December. See the AusPollen website for pollen forecasts from around Australia.

Research suggests that thunderstorm asthma is mostly triggered by an uncommon type of thunderstorm that causes grass pollen grains to be swept up into the clouds as the storm forms. When they absorb moisture, they burst open and release large amounts of smaller allergen particles. One pollen grain can release up to 700 of these smaller particles. These are then blown down to ground level, creating an outflow wind full of potential asthma triggers.

These particles are so small that they can be breathed deeply into the lungs. In some people this will cause the lungs to become irritated. Irritation can cause swelling, narrowing and extra mucus production in the small airways in the lung. This makes it difficult to breathe and can result in asthma symptoms such as wheezing, chest tightness and coughing. These asthma symptoms may become severe very quickly.

Not all thunderstorms in pollen seasons result in thunderstorm asthma. There have been six large thunderstorm asthma events in Melbourne over the last 35 years and each has occurred in November, which coincides with the peak grass pollen season. Large thunderstorm asthma events have also occurred in other parts of Australia and around the world.

These large instances are known as epidemic thunderstorm asthma events. They follow a particular type of thunderstorm that exposes a large number of people to high concentrations of the small allergen particles from burst pollen grains, over a short period of time. The result is the sudden onset of asthma in a large number of people, including many people who may never been diagnosed with asthma before.

Who is at risk of thunderstorm asthma?

Thunderstorm asthma can affect people living in metropolitan, regional or rural areas. It can affect people who have never been diagnosed with asthma.

Those at increased risk of thunderstorm asthma include people with a history of asthma, people with undiagnosed asthma (see below) and people with hay fever (particularly seasonal hay fever) or allergy to grass pollen.

Could I have undiagnosed asthma?

Asthma affects about 1 in 9 people and can start at any age. Many people don’t realise that you can develop asthma as an adult, so it is important to recognise asthma symptoms and see your doctor for review if you experience any of them.

The most common symptoms of asthma are:

  • wheezing – a continuous, high-pitched sound coming from the chest while you are breathing
  • shortness of breath – a feeling of not being able to get enough air
  • a feeling of tightness in the chest
  • coughing – alongside the other symptoms.

You do not need to have all of these symptoms to be diagnosed with asthma and they may come and go.

A diagnosis of asthma is more likely if you have eczema or hay fever, or have close relatives with allergies and/or asthma, and if your symptoms:

  • keep coming back, or happen at the same time each year
  • are worse at night or in the early morning
  • are clearly triggered by exercise, allergies or infections
  • improve quickly with reliever medication

Different people can have different triggers of their asthma. These can include:

  • ·viral respiratory infections (like the common cold);
  • indoor and outdoor air pollution (such as cigarette smoke or smoke from fires);
  • allergies (house dust mite, moulds, pollens, pets); and
  • exercise.

If you suspect you might have asthma, it is important to see your doctor for a professional diagnosis. Don’t ignore it – if you do have asthma, the sooner you get it under control, the sooner your lungs will improve, the better you will feel and the more prepared you will be for any further thunderstorm asthma events.

How can I prepare for thunderstorm asthma?

While it is currently difficult to predict a thunderstorm asthma event, there are a number of things you can do to be prepared.

If you have asthma, discuss the possibility of thunderstorm asthma with your doctor and include this in your asthma action plan.

If your asthma is triggered by pollens, and is worse in the spring and summer when hay fever is active, then it is important you have a current asthma action plan and that you regularly use a preventer medication, especially during this time. If you don’t use a preventer, see your doctor to discuss whether you would benefit from preventer treatment.

Remember preventers work slowly and can take up to a few weeks to work, and need to be taken every day

If you have both asthma and hay fever remember that better control and management of your hay fever can also improve your asthma control. Speak to your doctor about the benefits of asthma preventer medication, optimise your hay fever care and have an up to date asthma plan that includes thunderstorm asthma.

If you have symptoms that may be asthma then you should see a doctor to determine if you have asthma and develop a plan.

If you have hay fever during the grass pollen season, you should see your doctor to discuss the medications you use to manage your symptoms, such as over the counter anti-histamines and nasal corticosteroid sprays. You should also discuss any possible asthma symptoms you may have, what measures you should take to avoid thunderstorm asthma and the value of carrying an asthma reliever during pollen season.

What should I do if a thunderstorm is forecast in pollen season?

If you have been diagnosed with asthma, have symptoms of asthma or have a history of seasonal hay fever, be alert to the potential dangers of thunderstorm asthma.

Be aware of when thunderstorms are forecast particularly on HIGH or EXTREME pollen count days.

If you have asthma:

  • Where possible avoid the potential allergens blown on the winds of the approaching thunderstorm by staying indoors with doors and windows closed until the storm front has passed. However, remain alert for any asthma symptoms.
  • If you have been prescribed preventer medications, ensure you take it as advised by your doctor.
  • Always carry your reliever medication with you.  This is your emergency asthma first aid medication.
  • Know the signs of worsening asthma and the asthma first aid steps.
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    • If you start developing any signs of asthma, follow your asthma action plan. If you don’t have one get a blue reliever puffer (you can get these over the counter at any pharmacy) and follow the asthma first aid steps. If at any point you are concerned your asthma is rapidly worsening, please call 000 and say you are having an asthma attack.

If you have seasonal hay fever:

  • Where possible avoid the potential allergens blown on the winds of the approaching thunderstorm by staying indoors with doors and windows closed until the storm front has passed. However, remain alert for any asthma symptoms.
  • If you, or someone in your care, start developing asthma symptoms, do not ignore this and seek medical assessment and advice as soon as possible. If required and you have a blue asthma reliever puffer available, follow the steps for Asthma First Aid. Remember asthma reliever medication used in an emergency is unlikely to cause harm even if the person doesn’t have asthma.
  • If there are signs that a person’s condition is deteriorating, urgent care should be sought by calling 000. Signs of rapid deterioration include, little or no relief with their reliever puffer, they are unable to speak comfortably, or if their lips are turning blue. An asthma attack can be life threatening.

Other general tips for managing your asthma

  • If you have been prescribed a preventer, ensure you take it as advised by your doctor to keep your airways healthy and reduce the risk and severity of asthma flare-ups
  • If you also experience hay fever speak to your doctor or pharmacist about treatments. Better control and management of hay fever can improve asthma control. Regular use of nasal corticosteroid sprays is more effective than antihistamine tablets for severe hay fever, and both treatments can be used together.
  • Ensure you have a current asthma action plan - This written set of instructions, prepared by your doctor, is essential to help you recognise when your asthma is worsening and what to do about it.

How do I stay informed about weather and pollen counts?

Melbourne Pollen Count – grass pollen forecast

  • Produced by the School of Bioscience, University of Melbourne
  • Available at:
  • A free mobile device App (Melbourne Pollen Count and Forecast) provides notifications of high pollen forecast days to users.

Deakin University (AirWatch) – grass pollen forecast

Weather forecasts including forecast thunderstorms are available from the Bureau of Meteorology at: and by radio and television news updates.


How do I stay informed about asthma?

There are a number of ways you can manage your asthma and stay informed on weather and the pollen count for those with hay fever or asthma or both, whether it be via an app or contacting your local Asthma Foundation

Asthma Australia - Asthma App 

The Asthma App provides easy access to:

  • the latest asthma information
  • asthma medication and devices 
  • device technique videos 
  • asthma action plans 
  • asthma first aid steps
  • and the Australian Asthma Handbook clinical guidelines

Available from iTunes – look for the blue balloon

1800 ASTHMA (1800 278 426)

  • • Opportunity to speak to an asthma educator 
  • Education, information and support

Where to get help

  • In an emergency, always call Triple Zero (000)
  • The Emergency Department of your nearest hospital
  • Your doctor
  • NURSE-ON-CALL Tel. 1300 60 60 24 – for expert health information and advice (24 hours, 7 days)
  • Health Direct 1800 022 222
  • National Home Doctor Service Tel. 13 SICK (13 7425) for after-hours home doctor visits (bulked billed)

Information about asthma

Information about allergies

This page has been produced  in conjunction with Department of Health and Human Services Victoria and Australasian Society of Clinical Immunology and Allergy (ASCIA)

Last updated: December 2016

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