Australia is in the middle of a seasonal phenomenon that is little discussed but a regular source of multimillion-dollar insurance losses, the Bureau of Meteorology says.

Cool season tornadoes – or “coldies” – typically occur between May and September, when strong cold fronts and low-pressure systems move across southern Australia.

The bureau says they occur more often than many people realise, and southwest WA is among the world’s more tornado-prone regions, recording five to six each cool season. The true number is almost certainly far higher because many tornadoes occur in sparsely populated areas or are never reported.

While Australian tornadoes are generally much smaller and shorter-lived than those in the US – most lasting only 10-30 minutes – they can leave narrow paths of destruction stretching several kilometres.

A tornado in Perth’s Bicton suburb in May 2005 left insured losses of about $50 million. More recently, in May 2024, a storm in Bunbury damaged more than 200 properties.

The bureau says forecasting tornadoes remains difficult because of their small size and short lifespan.

While experts can identify broad areas where atmospheric conditions are favourable, warnings are generally issued only when a tornado is considered likely, radar indicates one may be occurring, or one has been confirmed.

There is no evidence tornadoes are becoming more common, and the bureau attributes a rise in reports to population growth, and greater use of smartphones and social media, making them more likely to be observed and documented.