Australia's second-largest city Melbourne was struggling to cope on Saturday with a once-in-a-century heatwave that has claimed dozens of lives and sparked wildfires that have razed up to 20 homes.
More than 500,000 houses and businesses in the city of five million were left without power on Friday night after an electrical substation exploded in the heat.
Emergency services were stretched to breaking point as dozens of people succumbed to heat-induced exhaustion.
Temperatures in Victoria state topped 43 degrees Celsius (109 Fahrenheit) for a record-breaking third consecutive day on Friday, when up to 20 homes and a timber plantation were destroyed in a 6,500-hectare (16,000-acre) blaze.
There was some relief on Saturday when the temperature dropped to a relatively comfortable 30 degrees in bay-side Melbourne, which is hosting the Australian Open tennis tournament.
But authorities said big fires continued to burn in the rural Latrobe Valley, 100 kilometres (62 miles) from the city, threatening a major power supply and a number of homes amid persistent 40-45 degree heat.
"These are unprecedented conditions. It's the hottest week since records began," said Victoria's state leader John Brumby.
Prime Minister Kevin Rudd called it an "ugly time."
"The southern part of the nation is a tinder box at the moment, it is just appalling," he said, reflecting upon the "terrible lessons of previous harsh Australian summers."
Earlier in the week, as the historic heat took grip, men's champion Novak Djokovic sensationally pulled out of his Australian Open quarter final with heat-related problems, the first defending champion to withdraw in the Open era.
Three-time champion Serena Williams, who will take on Russia's Dinara Safina in Saturday's women's final, described playing as an "out-of-body" experience before the roof of the Rod Laver Arena was closed and a row over the Australian Open heat policy ensued.
The heat was blamed for a spike in sudden deaths in the neighbouring state of South Australia, which was in the grip of its hottest weather since 1908 as temperatures exceeded 40 degrees for a fourth straight day on Saturday.
A total of 30 people, mostly aged older than 70, had perished in the heat by Saturday morning, with more recorded throughout the day, according to the state's ambulance service.
"We've noticed pretty much the same sort of pattern as yesterday where we've had a similar sort of workload, as far as unexpected and unfortunate deaths are concerned," an ambulance spokesman said, adding that they had received a record number of calls.
Emergency call-outs jumped by more than 70 percent in Victoria, with extra staff brought in to meet demand.
In Melbourne, the Friday power cut forced the cancellation of all trains. City buildings were evacuated, and rescue crews were called in to free workers trapped in office tower elevators.
Patients were turned away from overstretched hospitals running on reserve generator power.
"We're in uncharted waters, unprecedented conditions, and with the week and hot weather (we've had) some of these systems have never been designed to operate in 44-45 degree heat," Brumby said.
The unrelenting heat is forecast to continue for the next seven days, and could be sign of climate events to come, according to the World Meteorological Organisation.
"It is very likely that hot extremes, heatwaves and heavy precipitation events will continue to become more frequent as a result of climate change," it said.