Thunderstorm asthma – how do we prepare for this spring?

Judi Wicking 
Registered Nurse and Asthma and Respiratory Educator, National Asthma Council Australia

People who are allergic to ryegrass pollen can experience asthma symptoms during springtime thunderstorms in regions with high ryegrass pollen concentrations – even if they have never had asthma before.


Primary health care nurses can help reduce the risk of thunderstorm asthma in two main ways:

  • By ensuring that patients with ryegrass pollen allergies are taking preventive medication from October to December – this means intranasal corticosteroids for people with allergic rhinitis and inhaled corticosteroids for people with asthma.
  • By advising people at risk to avoid being outdoors in wind gusts during springtime thunderstorms. 

What happened in the 2016 Victorian thunderstorm asthma epidemic?

On the Monday evening of 21 November 2016 the world’s largest recorded epidemic thunderstorm asthma event occurred in and around Melbourne and Geelong.1 Hospitals, ambulance services, general practices and community pharmacies were overwhelmed by an influx of people with breathing problems.

Over several hours, hospital emergency departments were overloaded by high numbers of people presenting with asthma. Victorian authorities believe that at least nine people died in November as a result of thunderstorm asthma,1 pending the official findings of an inquiry by the Victorian State Coroner.

Thunderstorm asthma epidemics have previously occurred in Australia, predominantly in New South Wales, Victoria and the Australian Capital Territory.1–3 All occurred in October or November. 


Figure 1: One hypothesised mechanism of thunderstorm asthma. Storms might increase allergic reactions by breaking pollen grains into smaller particles that are more easily breathed in. Source: Marks et al (2001).7 Illustration courtesy of Alex Gonzales.




What, when and who?

What is it and what causes it? 

Thunderstorm asthma is an unusual cluster of allergic asthma flare-ups (including severe acute asthma) associated with springtime thunderstorms. It is not necessarily a special kind of asthma. However a certain type of thunderstorm appears to be needed, together with a high pollen count, to trigger this event. 

People who are allergic to grass pollen can develop asthma when they inhale outdoor air that contains a high concentration of pollen grains.4 Thunderstorms may increase the risk by breaking up pollen grains into very small particles that penetrate lungs more easily (see Figure 1), but this is not proven.2 Fungal spores may also contribute to thunderstorm asthma in some people.2

All thunderstorm asthma epidemics in Australia are thought to have been caused by the pollen of perenn ial ryegrass, a common pasture crop.2 High rainfall might contribute to thunderstorm asthma conditions by promoting ryegrass growth and pollination – the Victorian epidemic occurred following a period of unusually high rainfall (see Figure 2).

When does it occur?

The risk is greatest during the first 30 minutes of a thunderstorm, when there are usually gusty winds (see Figure 3). Symptoms can continue or worsen into the next day. 

Who is at risk? 

People with seasonal allergic rhinitis (hay fever) who are sensitised to ryegrass pollen (with or without known asthma) are at risk of thunderstorm  asthma.1,2,4 In Australia and internationally, at least 90% of recorded cases of thunderstorm asthma have occurred in people with a history of allergic rhinitis.2 During thunderstorm asthma epidemics, people with a previous diagnosis of asthma have the worst outcomes (e.g. life-threatening asthma or death).

People with asthma are at higher risk of having an asthma flare-up trigged by a thunderstorm if their asthma is poorly controlled or they are not taking regular preventer treatment with an inhaled corticosteroid.1,2 

People who do not have allergic rhinitis or asthma are at very low risk of thunderstorm asthma. 


Figure 2. High Victorian rainfall contributes to thunderstorm asthma conditions. Very high rainfall leading up to spring thunderstorms may have contributed to high pollen counts in the air. Source: Australian Bureau of Meteorology (2016).8 Reproduced with the permission of the Australian Bureau of Meteorology.




Figure 3. Emergency ambulance calls in Victoria, Monday 21 November 2016. The spike in emergency calls corresponded with the beginning of the storm. Source: Victorian Inspector-General for Emergency Management (2017).9 Reproduced with permission of the Victorian Government.



How can we stop it happening again?

Thunderstorm asthma could be reduced by; 

Identifying people at risk

Identifying people at risk because they are allergic to ryegrass allergy – this includes people with positive allergy tests and people who are very likely allergic because they have seasonal allergic rhinitis

Good hay fever control

Taking regular intranasal corticosteroid starting by 1 October and continuing through December. 

Good asthma control

Taking regular preventer treatment containing inhaled corticosteroids, if prescribed (especially important 1 October–end December) and having an up-to-date individualised written asthma action plan. 


Warning about the risk of springtime thunderstorms, avoidance advice, and asthma first aid. People at risk should avoid breathing outdoor air during a springtime thunderstorm, especially during wind gusts just before the storm breaks (See Table 1).

Table 1. People with allergy to ryegrass pollen (probable* or definite)
















Asthma and allergic rhinitis resources

Source: National Asthma Council Australia 20175
*Judi Wicking would like to acknowledge Jenni Harman for editorial assistance in the writing of this article.

Nurses will be hugely influential in the preparation, prevention and promotion of asthma and allergic rhinitis management for patients this pollen season. APNA has been involved in the public and health practitioner campaign preparation and will provide members with resources and information during the season.

1. Victoria State Government Department of Health and Human Services. The November 2016 Victorian epidemic thunderstorm asthma event: an assessment of the health impacts. The Chief Health Officer’s Report, 27 April 2017. Melbourne: Victorian Government; 2017.
2. Davies J, Queensland University of Technology. Literature review on thunderstorm asthma and its implications for public health advice. Final report. Melbourne: Victorian State Government Department of Health and Human Services; 2017. 
3. Waters J, Corbett S, Gibson P, et al. Epidemic asthma surveillance in the New England Region 1990-1992. Public Health Res Pract. 1993; 4.
4. D’Amato G, Vitale C, D’Amato M, et al. Thunderstorm related asthma: what happens and why. Clin Exp Allergy. 2016; 46: 390-396. 
5. National Asthma Council Australia. Epidemic thunderstorm asthma. An information paper for health professionals. Melbourne; 2017.
6. Australasian Society of Clinical Immunology and Allergy. Treatment plan for allergic rhinitis (hay fever). ASCIA; 2015.
7. Marks GB, Colquhoun JR, Girgis ST, et al. Thunderstorm outflows preceding epidemics of asthma during spring and summer. Thorax. 2001; 56: 468-471.
8. Australian Bureau of Meteorology. Victorian rainfall deciles 1 August to 31 October 2016. Melbourne: ABM; 2016 [cited 2017 July]; Available from:
9. Victorian Inspector-General for Emergency Management. Review of response to the thunderstorm asthma event of 21–22 November 2016. Final report. Melbourne: Victorian Government; 2017.

Article source: Primary Times Spring: Volume 17, Issue 3, 2017

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