Heat records across South Australia could topple on Thursday, as authorities warn dangerous conditions will make bushfires uncontrollable.
Adelaide is forecast to hit 45C, but the Bureau of Meteorology says the city's 80-year-old record high of 46.1C is within reach.
"You wouldn't rule it out," forecaster Jonathan Fischer told reporters on Wednesday.
The heat will intensify in the state's regional centres, with a high of 49C expected at Port Augusta, and 47C at Port Pirie and Roxby Downs.
"Nowhere is going to escape," Mr Fischer said.
"We will see records broken tomorrow, with many locations forecast to be near their maximum all-time record."
The Eyre Peninsula town of Ceduna already notched its hottest day on record on Wednesday when it reached a scorching 48.4C, while Adelaide topped 40C.
The temperature in the city is expected to drop to just 28C overnight before climbing on Thursday, when the metropolitan fire district will be one of 13 across the state under a total fire ban.
The Mount Lofty Ranges, the Kangaroo Island, Lower Eyre Peninsula and the Lower South East will experience extreme fire danger conditions.
CFS state duty commander Yvette Dowling urged the public to avoid risky behaviour in order to minimise the bushfire threat.
"If a fire does start with these forecast weather conditions, we're not going to be able to control that fire," she said.
"The communities are at risk, our firefighters are at risk, all emergency services are at risk tomorrow."
SA Health said the heatwave, which started on Tuesday, will be worse than last week's, when 69 people presented to SA hospitals with heat-related conditions.
Chief medical officer Paddy Phillips urged the public to drink plenty of water and avoid exercise or physical activity, while Council on the Ageing SA chief executive Jane Mussared urged older people to take extra care.
"The stress and anxiety of rising electricity costs can compromise decisions to turn on the air conditioner when it's hot, but I urge people to put their health first," she said.
"It is a good time for friends, family and neighbours to pop in on people they think may struggle in the heat."
The market regulator predicts the state will have sufficient electricity supply, but SA Power Networks cancelled most planned work for the day to focus on responding to outages.
Relief is not expected until Friday, when a cool change will bring a 31C high in Adelaide.
