Tropical cyclones are powerful, rapidly rotating storm systems. They're characterised by a low pressure centre and dangerous weather, including strong winds, heavy rain and thunderstorms.
Australia's tropical cyclone season runs from November to April. It is possible to see cyclones outside this time, but it is rare.
Within the Australian region, tropical cyclones start as low pressure systems over warm tropical waters to the north of our country. Australia's most cyclone-prone area is the northwest coast of Western Australia between Broome and Exmouth. But we do also see cyclones forming outside this area, including over northern Queensland and off the Northern Territory's Top End. And it's within these tropical areas where we are most likely to see direct impacts from a cyclone. But we can also feel the effects for places as far south as Perth and also northern New South Wales.
Cyclones need 4 main ingredients to form.
- First, warm water of at least 26.5 °C. This acts as fuel for a tropical cyclone.
- Second, an area of unsettled weather such as a low pressure system which becomes the focus of cyclone formation.
- Third, an atmosphere that supports thunderstorms. Lots of warm rising tropical air fuelling thunderstorms which gives strength to a cyclone.
- But how do these ingredients actually come together to form a cyclone? Well, as the Earth rotates, it generates forces that causes winds to flow clockwise around a low pressure system or area of unsettled weather in the southern hemisphere. And this causes a cyclone to spin. These forces are weakest near the equator itself. And so, we don't typically see cyclones forming within about 500 km of the equator. As developing cyclone starts to spin, it starts to pull in warm moist air that spins into the centre of the cyclone. As warm moist air moves in, it starts to spin even faster and wind speeds increase. When the wind blows at 63 km an hour, more than halfway around the centre for at least 6 hours, the system is named a tropical cyclone. Warm air drawn into the centre, then rises, and then cools. This causes clouds to form that draw in more warm, moist air to further strengthen the cyclone.
Cyclones are categorised by their wind speed. Category 1 cyclones have wind gusts up to 125 km an hour, while category 5 cyclones, the strongest, have wind gusts of more than 280 km an hour.
Satellite footage shows what a tropical cyclone looks like from above. And we can see the classic rainbands spiralling clockwise into the centre of the cyclone. Within these spiral rainbands, we see air rising and condensing to form rain and thunderstorms.
And if cyclone reaches category 3 strength or higher, these spiral bands may wrap tightly enough around the centre to form an eye. And it's near the eye wall where we do see the strongest winds as well as heaviest rain. But in the eye itself, this is an area of relative calm. We see light winds and also sometimes clear skies.
Within the cyclone, strong winds can cause significant damage, but wind isn't the only hazard. And so tropical cyclone categories on their own don't tell you how severe the impacts could be.
Heavy rain is another hazard. And although cyclone wind speeds do decrease as it moves over land, heavy rain can continue, causing devastating flooding.
Cyclones with the strongest wind speed don't necessarily bring the heaviest rain. And so it is possible for a category 1 cyclone to cause worse flooding than a category 5 cyclone.
In addition, storm surges are also dangerous. These are caused by winds and low pressure when the sea rises above the expected tide. When this happens close to the highest tide level of a year, this can swamp low-lying areas and flow for kilometres inland.
The Bureau forecasts cyclones and warns you about them so you can prepare and stay safe. If you live or travel to areas which could be impacted by cyclones, it is important that you have the latest information. You can check this information on the Bureau's website or on the BOM weather app.
And on the BOM Weather app, you can set up notifications to get warnings direct to your phone. And to learn more about tropical cyclones, be sure to visit the tropical cyclone knowledge centre on our website.
Australia's tropical cyclone season runs from November to April. It is possible to see cyclones outside this time, but it is rare.
Within the Australian region, tropical cyclones start as low pressure systems over warm tropical waters to the north of our country. Australia's most cyclone-prone area is the northwest coast of Western Australia between Broome and Exmouth. But we do also see cyclones forming outside this area, including over northern Queensland and off the Northern Territory's Top End. And it's within these tropical areas where we are most likely to see direct impacts from a cyclone. But we can also feel the effects for places as far south as Perth and also northern New South Wales.
Cyclones need 4 main ingredients to form.
- First, warm water of at least 26.5 °C. This acts as fuel for a tropical cyclone.
- Second, an area of unsettled weather such as a low pressure system which becomes the focus of cyclone formation.
- Third, an atmosphere that supports thunderstorms. Lots of warm rising tropical air fuelling thunderstorms which gives strength to a cyclone.
- But how do these ingredients actually come together to form a cyclone? Well, as the Earth rotates, it generates forces that causes winds to flow clockwise around a low pressure system or area of unsettled weather in the southern hemisphere. And this causes a cyclone to spin. These forces are weakest near the equator itself. And so, we don't typically see cyclones forming within about 500 km of the equator. As developing cyclone starts to spin, it starts to pull in warm moist air that spins into the centre of the cyclone. As warm moist air moves in, it starts to spin even faster and wind speeds increase. When the wind blows at 63 km an hour, more than halfway around the centre for at least 6 hours, the system is named a tropical cyclone. Warm air drawn into the centre, then rises, and then cools. This causes clouds to form that draw in more warm, moist air to further strengthen the cyclone.
Cyclones are categorised by their wind speed. Category 1 cyclones have wind gusts up to 125 km an hour, while category 5 cyclones, the strongest, have wind gusts of more than 280 km an hour.
Satellite footage shows what a tropical cyclone looks like from above. And we can see the classic rainbands spiralling clockwise into the centre of the cyclone. Within these spiral rainbands, we see air rising and condensing to form rain and thunderstorms.
And if cyclone reaches category 3 strength or higher, these spiral bands may wrap tightly enough around the centre to form an eye. And it's near the eye wall where we do see the strongest winds as well as heaviest rain. But in the eye itself, this is an area of relative calm. We see light winds and also sometimes clear skies.
Within the cyclone, strong winds can cause significant damage, but wind isn't the only hazard. And so tropical cyclone categories on their own don't tell you how severe the impacts could be.
Heavy rain is another hazard. And although cyclone wind speeds do decrease as it moves over land, heavy rain can continue, causing devastating flooding.
Cyclones with the strongest wind speed don't necessarily bring the heaviest rain. And so it is possible for a category 1 cyclone to cause worse flooding than a category 5 cyclone.
In addition, storm surges are also dangerous. These are caused by winds and low pressure when the sea rises above the expected tide. When this happens close to the highest tide level of a year, this can swamp low-lying areas and flow for kilometres inland.
The Bureau forecasts cyclones and warns you about them so you can prepare and stay safe. If you live or travel to areas which could be impacted by cyclones, it is important that you have the latest information. You can check this information on the Bureau's website or on the BOM weather app.
And on the BOM Weather app, you can set up notifications to get warnings direct to your phone. And to learn more about tropical cyclones, be sure to visit the tropical cyclone knowledge centre on our website.
Understanding tropical cyclones
10 November 2025
Tropical cyclones are powerful, rapidly rotating storm systems. Learn about when, where and how they form in the Australian region so you can be prepared.