South Australians, including those attending Friday's Big Day Out in Adelaide, have been warned to take care during the state's second heatwave this year.
"The reality for South Australians is that we are in day three of what is likely to be a very protracted period of very hot weather," State Emergency Services (SES) chief officer Chris Beattie said on Thursday.
"Daily maximums and overnight minimums have been forecast to escalate from today throughout the weekend.
"Although there is a slight cool forecast for Monday, all indications are that the extreme heat will then continue next week."
The SES has issued an indefinite extreme heat warning for the state and has extra crews on alert throughout the state.
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The Bureau of Meteorology revised its forecasts for Adelaide to allow for cooling to about 30C on Monday, but the city is facing at least five days during next week with temperatures above 40C.
The city sweltered through a heatwave earlier in January when the mercury was higher than 40C for five consecutive days.
The SES has advised people to take appropriate precautions including drinking plenty of fluids, staying indoors and never leaving children or pets unattended in cars.
About 25,000 people are expected to attend the Big Day Out at Bonython Park on Friday.
Superintendent Chris Baulderstone said police would be watching out for drug use and antisocial behaviour, and warned that people's safety remained in their own hands.
"It's going to be very hot, so we remind those attending to stay hydrated," he said.
"On a 40-degree day, water is your best option. Alcohol and extreme heat aren't a good mix."
Steve Cameron from SA Ambulance Service advised attendees to not only take care of themselves, but to take care of their mates and get help immediately at the first sign of difficulty.
