Heat waves are to most people something of a novelty, an excuse to hit the beach. But in truth they kill more Australians than road accidents.
The hot conditions have been breaking records nationwide this summer, with Tasmania and NSW recording their highest ever temperatures and the Northern Territory suffering more consecutive 40-plus days than ever before.
The heat is set to rise again next week with a second high on the way and experts say those who feel they are immune could be most at danger.
Dr Liz Hanna, of the Climate Change Adaptation Research Network – Human Health at the Australian National University, says we vastly overestimate our ability to cope with heat.
"Heat alone already kills more Australians than the road toll. If it is not already double, it soon will be."
Official figures from the Government's Climate Change Health Risk Assessment show that thermal extremes contributed to the deaths of approximately 1121 people in 2002 in major Australian cities. This figure is expected to reach 2030 people by 2020.
On Australian roads in 2011 there were 1102 deaths, a figure that is dropping steadily every year.
"There is an upper limit to human tolerance of heat. We begin to feel ill when our body temperature reaches 38 degrees," Dr Hanna says.
Related: Eight weird ways to survive the heat
Our metabolism and moving muscles generate heat which must be expelled to regulate our temperature. This starts to become difficult when the air temperature goes above 30 degrees, and our system is compromised when it reaches 35 or more — like a freezer with the door left open.
Most people cannot sustain physical exercise beyond a few minutes in very high temperatures without experiencing what's known as heat gain, when we lose the ability to cool ourselves, or thermoregulate.
Heat gain places great strain on the heart, which is why the elderly, young and those with heart conditions are particularly vulnerable.
"The temperature at which we succumb will vary according to the humidity, our familiarisation with hot conditions, our level of exposure to the heat, plus our level of heat generation via exercise," said Hanna.
She warns it is vital to keep the body temperature down and trying to battle through the heat is not safe for anyone.
"Physical exercise generates heat, and so our body tells us to slow down and rest. We feel lethargic. This is a survival mechanism, and should not be disregarded," she says.
"Workplace and family duties that compel us to keep moving exacerbate our risk of overheating. We should not underestimate the seriousness of heat stress.
"Overheating can and does kill, even the young and fit. However, the most vulnerable to heat include the elderly, those with heart conditions and the very young. People who cannot access cooled environments are also at risk. The response of turning on air conditioners only exacerbates the problem of global warming. The only correct response is to slow down, and ultimately reverse, the warming."
Ambulance Service of NSW acting chief superintendent Ian Johns says reports from paramedics in the field this week suggest people have been adhering to safety messages.
"We're heartened by reports that many people braving the heat are carrying water bottles. We're also hearing reports of reduced activity in places that are usually well-frequented.
"We believe people across NSW have heeded the warnings and they’ve done really well in their preparation."
Dr Hanna still warns that our attitude to heat is unnatural and unsustainable — we don't see it as a worthy interruption to daily life.
"Overheating can and does kill, even the young and fit."
"The response of turning on air conditioners only exacerbates the problem of global warming. The only correct response is to slow down, and ultimately reverse, the warming."
Author: Philippa Lees
Approving editor: Rory Kinsella.