The Bureau of Meteorology will roll out a pilot of its new Heatwave Warning Service early next year to alert people across the country to what some call “the silent killer”. Excessive heat causes more deaths than other hazards such as bushfires, cyclones and floods, research has found.

John Nairn, weather services manager at the bureau’s Adelaide office and project manager for the warnings, said the level of the alerts – including severe and extreme - will be based on how far conditions are expected to depart from historical mean temperatures for a particular area, and from the warmth over the preceding 30-day period.

Northern Tasmania, for instance, would typically see a heatwave warning triggered at a lower temperature than regions more accustomed to heat stints, such as the Pilbara in WA.

“Are you prepared for what you’re about to be inflicted with, and to what degree?,” Mr Nairn said.

The need for such a service was underscored earlier this year, with Australia recording its hottest day, month and season. It has also smashed rolling 12-month heat records and remains on course to register its hottest calendar year.

“There was pretty much a heatwave somewhere in the country all summer long,” Mr Nairn said.

Inceasing risk

Alasdair Hainsworth, assistant director for weather services at the bureau, said Australia - and much of the rest of the world – was seeing a rise in temperatures, making heatwaves more likely in the future.

“We know these extremes are becoming more frequent and the time is right is develop a service along these lines,” Mr Hainsworth said.

The information, to be automatically generated and displayed on the bureau’s website, is expected to benefit a wide range of the users, such as emergency services, outdoor workers and those planning sporting activity. Significantly, the health impacts from excess heat may have more to do with overnight rather than day-time extremes.

“Minimum temperatures are probably more important than maximum temperatures during a heatwave,” Mr Nairn said. “If you’re not able to discharge the heat that you’ve accumulated during the day, you’ll carry forward whatever you’ve stored into the next hot day.”

At the height of summer, the shorter nights add to heatwave risks as do slow moving weather systems leaving hot air circulating over the same spot. Soils, though, can also play a key role in determining the severity of the heat.

“Dry soils are really important in terms of driving extreme heatwaves or longer period,” Mr Nairn said.

While it is too early to determine which parts of Australia are likely to suffer heatwaves this summer, parts of Queensland now in drought are at risk of a repeat of the 2004 heatwave over the state’s south-east, Mr Nairn said. NSW, which has also been hit by abnormal heat and below-average rainfall, faces similar conditions.

“Until the monsoon breaks, they’re at some level of risk of an extreme (heatwave) event,” Mr Nairn said.Mr Nairn’s work has attracted wide international interest, with his methodology being adopted by the World Meteorological Organisation.