Adelaide'shot weather record set in 1939 could be broken on Thursday.
The Bureau of Meteorology (BOM) is predicting a top of 45 degrees Celsiusfor January 24, just one degree shy of the 46.1C record for West Terrace in Adelaide's CBDset on January 12, 1939.
It reached 45.7C at the BOM's old Kent Town office on January 28, 2009.
BOM state manager John Nairn said Thursday would be a "horror day".
"We are anticipating a temperature that is going to be quite challenging," he said.
"We're going to have very hot overnight conditions — probably most of the night will be in the low 30s.
"We'll dip to about 28C so it's going to be a hot night."
BOM meteorologist Philip Perkins earlier told ABC Radio Adelaide Thursday would be "an absolute stinker" — and that was when the forecast was 44C.
"We're starting to flirt with some records," Mr Perkins said.
A cool change is expected early on Friday.
"Hot days, we start to get used to that, but it's the nights where we can't recover," Mr Perkins said.
"We can't hydrate and have some good rest so we'll be… reaching for some coffee and all sorts."
The State Emergency Service (SES) has issued an extreme heatwave warning urging people to stay indoors if possible and to drink plenty of water.
"People should be very wary… over the next few days… to make sure they do not leave children or pets in a parked car even with the air conditioning running and the windows open," spokesman Jon Carr said.
Looking back on 1939
January 10 and January 12 in 1939 were the two hottest days in Adelaide since 1858.
Kings Park resident Harold Sammells, 101, was 21 in 1939 and remembered the day as "bloody hot".
"We had a whole week of it really, not just a day," he told the ABC.
"The whole week was well over 100 degrees [Fahrenheit — 37C].
"It was too hot to stay in the house… when the evening came, we were out on the front lawn."
He said steel power poles softened in the heat and bent over in the wind.
"Of course, after that, they changed them to the new stobie poles," he said.
Bushfires, ice shortages and shorts
Bushfires hit the Adelaide Hills and ice had to be rationed after machinery broke down at the government's Ice and Cold Storage Works in Light Square, in central Adelaide,because of the heat.
Adelaide newspaper The News reported that on January 10, another hot day, the weather bureau received 1,414 calls asking what the temperature was.
"Inquiries were disposed of in less than 10 seconds. In relays, officials took turns at the phone, calling '112.8' every time it buzzed," the newspaper reported.
Another report said men were switching to "lightweight suits" to cope with the heat.
"A few brave men defied tradition by going to work in shorts and white-duck suits, but most men lack the courage to set a fashion and to risk the ridicule of their fellow workers," the newspaper wrote.
"They confine their protests to discarding coats and vests, taking off collars, or wearing open-necked shirts."
Outback records set last week
Tarcoola and Port Augusta broke their temperature records last week.
The BOM said Tarcoola, in South Australia's north-west, reached 49C at 3:20pm on January 15, its hottest temperature since records began in 1903.
Port Augusta — a much larger town — also broke its record with a top of 48.9C at 2:31pm.
The top temperature ever recorded in Australia was 50.7C in Oodnadatta in January 1960.ABC