Victorians facing a stretch of days hotter than 40C are being urged not to underestimate the dangers of severe heat.
The state government issued a heat health alert as the mercury is expected to top 40C on Tuesday, Thursday and Friday.
A similar heatwave in January 2009 contributed to 370 deaths in Victoria and raised metropolitan ambulance callouts by about 50 per cent on the hottest days, according to the Department of Health.
The risk of bushfires will also grow in coming days, with a combination of heat and wind making Friday a potentially disastrous day.
Fire Services Commissioner Craig Lapsley said this heatwave marked the turning point of the Victorian summer.
"This is the time for people to revisit their (fire safety) plans. This is the time for people to start to think about their safety not only for this week but the remaining part of the summer," he said.
"Leaving early before a fire starts is the safest option, without a doubt."
The soaring temperature will bake remaining moisture out of bush and grasslands across Victoria.
"The finest fuels will be dried to a point where they are then available for any fire for the remaining part of the summer," Mr Lapsley said.
Health Minister David Davis called on the community to look out for the elderly, disabled or people who live alone.
"There's a need to make sure we check on our neighbours," he said.
He urged Victorians to keep up their fluids and stay cool during the hottest part of the day, between late morning and late afternoon.
"Spend as much time as you think is reasonable in cool or air-conditioned locations nearby, shopping centres, libraries or cinemas," he said.
He said night-time temperatures would also be high.