South Australia is bracing for its longest burst of extreme heat for more than three years with temperatures surging into the mid-40s in some regional centres.
The Bureau of Meteorolgy says much of the state will experience heatwave conditions with five days over 35 degrees Celsius.
In Adelaide, the mercury is expected to hit 40C on both Thursday and Friday, ahead of a milder change.
But temperatures will go higher in many regional centres with Nullarbor, on the west coast, to have 45C on both Wednesday and Thursday.
Senior Meteorologist Simon Timcke said after a couple of milder summers, SA was set to have its longest streak of very hot days since December 2019.
At that time, Adelaide had four days above 35C in the middle of the month then six days above 35C at the end of the month.
"We've got a big mass of very hot air up over the northwestern and central part of the continent," Mr Timcke said.
"We did get a burst of hot weather last week but a change pushed that hot air back over the far north of SA.
"But once the high pressure system currently south of the bight moves out east of Tassie, that will turn the winds around northerly and drag all that hot air back down over southern parts of the state."
The conditions will also lift the bushfire risk, with Friday shaping as the worst day with winds increasing as the change pushes through.
Mr Timcke said the timing of the cooler change was still somewhat unclear.
The forecast has prompted SA Health to urge everyone to take steps to stay cool inside and to avoid outside activity if possible, especially at the hottest part of the day.
SA Health said early signs of dehydration and heat-related illness included heavy sweating, having a raised body temperature, feeling dizzy or faint, fatigue, reduced appetite and increased thirst.
A more serious condition, heatstroke, was also possible and required urgent medical attention.
Signs of heatstroke included a dry and swollen tongue, sudden rise in body temperature to greater than 40C, disorientation or delirium, convulsions and a rapid pulse.
"The heat affects everyone but certain groups such as babies and young children, pregnant women, the elderly and people who have chronic health conditions are more at risk than others," Chief Public Health Officer Nicola Spurrier said.
"And it's important to check on your loved ones during hot weather, particularly if they live alone."
