Hot weather has caused more hospitalisations than bushfires in Western Australia in recent years, with parts of the state now sweltering through a second heatwave in as many weeks.
Bureau of Meteorology (BOM) forecaster Jessica Lingard said 267 people presented to hospital between 2020 and 2022 compared to eight from storm-related injuries, 21 from extreme cold and 42 from bushfires.
"That's almost five times as many as bushfires, and almost four times as many if you take in all of the others added together," she said.
Ms Lingard said a new system to define heatwaves was introduced in 2022 as the previous definition was based on city conditions.
"A heatwave was defined as three days of 32 degrees (Celsius), and that worked really well in the city," Ms Lingard said.
"But if you lived anywhere else in WA, three days over 32C ... it's pretty much just, you know, October through to April."
Sewage in water drops
The temperature reached at 39.9C in Perth on Thursday, and is forecast to peak at 41C on Friday and Saturday, and remaining in the high 30s into next week.
On Wednesday when the temperature nudged 36C, the heat had authorities on high alert, with two emergency bushfires igniting in the Bullsbrook area.
In Bullsbrook's town centre, authorities say the rising temperatures caused mulch at the local high school to spontaneously combust.
Hundreds of students and staff were evacuated from Bullsbrook College as the blaze threatened the school and nearby homes.
Dozens of firefighters and several aircraft were deployed to bring it under control.
The fire has now passed, but residents in the area are being told to be careful after sewerage wastewater was unintentionally dumped on properties in the fire's path.
"DFES Helitaks drew from water sources that have been identified as sewerage wastewater holding ponds," the Department of Fire and Emergency Services said in a statement on Thursday.
"People in the impacted area do not need to be alarmed. The forecast high temperatures will assist in neutralising any residual bacteria."
People in the impacted area are being asked to empty their water tanks, hose down their cars and carefully wash produce grown in their yards.
Health Minister Amber-Jade Sanderson said the risk of contamination was "very low".
"It was not dropped on homes," she said.
"There's a small risk that it may have dropped on people's gardens.
"It was dropped on bushland to fight that fire, and the contamination risk is very low."
At the height of the fire, Jono Clark, who was in the area with his water delivery truck, dumped thousands of litres on his neighbours' verges, stopping the blaze from spreading.
"I just kept going back and forward and it was pretty hectic there at one time and it was pretty hot," he said.
"I think the fire was very close, but that's what you do … when people are under threat."
How do you define a heatwave?
It depends on where you live.
Ms Lingard said the science of a heatwave was basically a long mathematical equation.
"A heatwave occurs when the maximum and minimum temperatures are unusually hot over a three-day period at a location," she said.
"That's the important bit — it is considered in relation to the local climate, and also the past weather at this location.
"So what makes a heatwave in Albany is different to what makes a heatwave in Geraldton, and different again to what makes heatwave in Broome, because we take into account what you're used to in that area."
Ms Lingard said acclimatisation was also a factor taking into account conditions over the past 30 days.
"A heatwave in February is different to a heatwave in November, because we're more used to hotter weather by the time we got to February than we are when we've just come out of winter and started to move through spring," she said.
Ms Lingard said people should seek relief from the heat as much as they can.
"We encourage people to seek cooler spaces in the community, your libraries, your shopping centres ... even just going to visit friends and family," she said.
Take care at Lunar New Year, music festivals
Department of Health data shows 51 people presented at emergency departments across the state during the last heatwave between January 29 and February 2 — up from 30 presentations the week prior.
WA Health's director of disaster preparedness Tudor Cordreanu said while the current heatwave was not classified as "extreme", it would affect a large amount of people.
"Its main effects are not as much on the size of the geography of the state, but on the number of the population — this is going to affect around about 70 per cent of WA population," Dr Cordreanu said.
"And we know that heatwaves are the number one killer as far as natural disasters are concerned."
Dr Cordreanu urged West Australians attending events, like festivals and Lunar New Year celebrations this weekend, to protect themselves from the heat by hydrating and staying in the shade or air conditioning.
"They [organisers] have mandatory legal obligations to ensure that the safety and the medical component of any mass gatherings is addressed properly," he said.
"We provide advice, but implementation is down to the organisers and the city themselves."
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