Health authorities are warning South Australians to brace for extremely hot conditions, with temperatures remaining high until the weekend.
The Bureau of Meteorology (BOM) expects the mercury in Adelaide to soar to 36 degrees Celsius tomorrow and 38C on Wednesday before a double dose of 40C on Thursday and Friday.
Meanwhile, temperatures could reach 42C in the state's Mid-North by Thursday, and into the mid-40s in the APY Lands.
BOM meteorologist Jenny Horvat said temperatures would remain high.
"Currently, we have heatwave warnings out for South Australia, and that includes an extreme heat warning for the West Coast and Lower Eyre Peninsula," she said.
"We are going to see that heat that is in the north and west currently move broadly across the state as we move across the week.
"That's driven by a high-pressure system that will be in the Tasman Sea directing a northerly air stream across the state."
This is the same high-pressure system creating extreme temperatures across Victoria and Tasmania.
Ms Horvat said there was still "uncertainty" about the timing of the change which is expected to come across from the west on Friday and possibly bring rain and thunderstorms.
SA Health Chief Public Health officer Nicola Spurrier said South Australians needed to look after each other.
"I know it hasn't been that hot up until this time and it's important we all think about that change in the temperature," she said.
"People can get quite sick if they don't keep up their fluids and they spend a lot of time standing out in the sun.
She advised South Australians to wear a hat, sunscreen and sunglasses.
"For many people, it's more serious," she said.
"People who've got chronic health problems, kidney problems, heart problems, lung problems, as well as older and pregnant people and children, are at greater risk.
"It's important if you have people like that in your family that you check up on them. And if you're in that situation yourself, it's worth having a conversation with your doctor about managing fluids.
"It's much better to stay indoors and have your air conditioner going."
The highest temperature recorded in South Australia today was at Oodnadatta, which hit 43.6C, while Coober Pedy reached 41.9C.
Adelaide reached a maximum temperature of 34.5C.
