Thunderstorm Asthma Peaks Before the Rain. Get Inside When the Gust Front Comes

The warning that matters usually arrives before the rain. On a hot, windy day with high grass pollen, thunderstorm asthma peaks in the gust front that runs ahead of the storm, when the wind picks up and the light changes. The rain comes later. By then the particles that cause the trouble have already been released. The sequence is worth holding onto, because it changes what you watch. On a high-pollen day, the sky going dark is not the first warning. The wind arriving is.

Two things catch people out. The first is the timing. The instinct is to wait for the storm, or to shelter once it starts. The second is the assumption that you need a diagnosis. Current asthma, past asthma, undiagnosed asthma and spring hay fever all sit in the risk group, and a person with no diagnosis can be affected. That last group is the difficult one. A sensitivity can go unnoticed through ordinary springs and only show up when a storm concentrates the pollen into particles small enough to reach the lower airway.

The official advice is short. Go inside before the gust front, close up, turn off any cooling that brings outside air in, and use a reliever early if you have one. Call 000 if the person is not breathing, getting worse, not improving after first aid, or if any other 000 trigger applies.

How a storm makes asthma

The mechanism starts with pollen. Grass pollen is swept up from the ground and carried in the air ahead of a thunderstorm. Some grains burst in the wind gusts just before the storm, releasing particles small enough to reach deep into the lungs. That is why the danger is concentrated in the wind before the rain, and why the first drop is not the signal to act. Particle size is the problem. Pollen grains on their own are too large to travel far into the respiratory tract. The burst changes that. It breaks the grain into fragments that can be inhaled past the nose and throat, and the wind carries them in a concentrated cloud rather than a diffuse background count.

The pattern explains the timing. A hot, dry, windy day lifts pollen. The gust front arrives with the first strong wind of the change. The grains burst. People who are sensitive breathe the particles in. The storm can then produce a rapid spike in asthma attacks across a whole region at once, which is what makes thunderstorm asthma different from an ordinary bad pollen day. There is also a difference in scale. An ordinary high pollen day affects the people who are sensitive to that pollen, spread across a city and a day. A thunderstorm can concentrate the same exposure into a short window, and that is why it can affect many people at once.

Rain and pollen have a more complicated relationship than the timing suggests. The guide to rain and pollen explains why a shower can help some allergy days and make others worse.

Who is at risk? Current asthma, past asthma, undiagnosed asthma and spring hay fever. ASCIA notes that around one in four people with hay fever also have asthma. That overlap is the reason a warning is not only for people who already carry a reliever.

The ten minutes before the rain

healthdirect’s wording is worth keeping: stay inside, especially when it is windy before the rain. The sequence below is the practical version.

1. Go inside before the gust front. Do not wait for the first drop.
2. Close doors and windows.
3. Turn off any air conditioner that brings outside air in, including evaporative cooling. If it cannot be turned off, set it to recirculate.
4. Stay inside until the storm has passed.
5. Do not rely on a mask.

The order matters. Going inside is the first move because it removes you from the air carrying the particles. Closing up is the second because it keeps that air from following you in. Turning off outside-air cooling is the third because a system can keep pulling the same air through the house after the doors are shut.

Point three is the one most often missed. An evaporative cooler pulls outside air through the house, which is the opposite of what you want when the air is carrying pollen particles. A refrigerated system set to recirculate is a different case, because it is not drawing in fresh air from outside. The test is simple: is the system bringing outside air in? If yes, turn it off.

Masks do not solve this one. It is a reasonable assumption, because masks work for so many other things, but healthdirect is clear: face masks do not protect you against the tiny particles. They are small enough to pass through the material and reach the parts of the lung where the reaction happens. A mask is not a substitute for going inside.

Staying in until it passes matters as much as the first move. The gust front is not a single moment. The wind can stay strong for a while, and the particles remain in the air.

The reliever, exactly

If you have an asthma action plan, follow it. That plan was written for you and it comes first. If you do not have one, the national first aid steps for people aged 12 and over are the ones to know, and they are worth reading before you need them. The sequence is designed to be used while you are waiting for help, not instead of it. It is short enough to keep on the fridge or in a phone note.

1. Sit the person upright.
2. Shake the puffer before every puff, then give 4 separate puffs through a spacer, one puff at a time, with 4 breaths after each puff.
3. Wait 4 minutes.
4. If there is no improvement, repeat once with another 4 puffs.
5. Call 000 if there is no improvement after the second round.
6. Keep giving 4 puffs every 4 minutes until help arrives.

Those steps come from Asthma Australia’s asthma first aid guidance. The simplified version was published in July 2025, and the blue reliever poster carries the continuing doses. The numbers are the national sequence, not a household guess: 4 puffs, 4 breaths per puff, 4 minutes, repeat once, then 000 if there is no improvement.

Call 000 if the person is not breathing, if the asthma is suddenly worse or not improving, if there is no reliever available, if you are unsure whether it is asthma, or if the person has known anaphylaxis. In that case, use the adrenaline autoinjector first.

The steps assume a spacer is on hand. If there isn’t one, Asthma Australia’s guidance is to use the puffer directly, one puff at a time with a slow, deep breath, but a spacer is the preferred method.

Children follow their own action plan. For everyone, the expiry date is easy to forget until the day you need it. The guide to what belongs in a first aid kit covers that check and the rest of the kit.

Where the warning comes from

The Bureau of Meteorology forecasts the storm. It does not issue the asthma risk forecast. That distinction matters, because a weather forecast can tell you a change is coming without telling you whether the air is carrying the kind of pollen that causes an epidemic. A severe thunderstorm warning and an epidemic thunderstorm asthma warning answer different questions, and one does not replace the other.

Victoria runs a detailed system. The Department of Health’s epidemic thunderstorm asthma risk forecast runs from 1 October to 31 December each year, covers nine districts, and uses three levels: green for low, orange for moderate and red for high. The current day’s forecast is updated about 12:30pm, and warnings are issued through VicEmergency. The department’s advice is to avoid any storm that forms, above all the wind gusts ahead of it. Once inside, shut the windows and doors and switch off cooling that draws outside air in.

The colour is a district-level guide, not a reading for your street. Green means low risk, not no risk, and orange or red is a prompt to change the day rather than a guarantee that a storm will form. The value is in the timing: the forecast is published before the change arrives, which is exactly when the ten-minute sequence is useful.

The forecast follows district lines, and the guide to Melbourne's unpredictable climate explains why the weather changes so quickly there.

The other states and territories publish their own information.

Check the forecast in the morning on any hot, windy spring or summer day, note the district, and decide before lunch what the afternoon looks like. That is easier than making the call while the wind is already up.

The forecast is a risk estimate, not a promise that your suburb will be hit. These events are rare, and most storm days pass without one. The right response is to stay in and be ready, not to treat every summer storm as a disaster.

After the storm

Symptoms can follow the storm, and they can appear in people who felt fine while it passed. Keep the reliever with you for the rest of the day. If breathing is still difficult after the storm, treat it as a reason to seek help rather than a reason to wait. A reliever used more than usual is worth mentioning at that appointment. So is a first episode of wheezing, even if it settled on its own.

See a GP if you have symptoms you have not had before, or if hay fever is affecting sleep or daily life. The longer game is to manage hay fever and asthma through the season, not only on the days with a warning. That means a current action plan, a reliever that is in date, and hay fever treatment that keeps the condition controlled.

None of that is a cure, and no single storm day is the whole risk. The point is to be less exposed when the conditions line up.

The days after a storm are also a good time to check the plan itself. If the reliever was hard to find, or the spacer was in another room, move it now. A plan that only works when everything is in the right place is not much of a plan.

The Ten Minutes Before the Storm

The ten minutes before the storm are the ones that count. Go inside, close up, turn off any cooling that pulls outside air in, and stay in until it passes. Do not wait for the rain to make the decision for you.

If you have a reliever, use it early. If the person is not breathing, getting worse, not improving after first aid, or any other 000 trigger applies, call 000. The forecast gives you notice. The sequence is what you do with it.

Sources: Better Health Channel, Thunderstorm asthma (https://www.betterhealth.vic.gov.au/thunderstorm-asthma); healthdirect, Thunderstorm asthma (https://www.healthdirect.gov.au/conditions/lung-and-respiratory-diseases/thunderstorm-asthma); Victorian Department of Health, Epidemic thunderstorm asthma risk forecast (https://www.health.vic.gov.au/environmental-health/epidemic-thunderstorm-asthma-risk-forecast); Asthma Australia, Simplified asthma first aid (https://asthma.org.au/wp-content/uploads/2025/07/AA25-Simplified-Asthma-First-Aid_WEB.pdf); Asthma Australia, Asthma first aid: blue reliever (https://asthma.org.au/wp-content/uploads/2021/12/AA26-Blue-1st-Aid-A4_Web-1.pdf); ACT Health, thunderstorm asthma public health alert (https://www.act.gov.au/health/public-health-alerts/public-health-alert-pages/public-health-alert-thunderstorm-asthma-event); NSW Health, Thunderstorm asthma (https://www.health.nsw.gov.au/environment/factsheets/Pages/thunderstorm-asthma.aspx)