South Australia is in the grip of a mini heatwave with temperatures to push into the low to mid 40s until at least the weekend.
The severe conditions are set to test the state's energy network but authorities are confident electricity supplies will be adequate.
The hot weather has also prompted a warning to international visitors in Adelaide for cycling's Tour Down Under to take care, while the state government will supply extra services to help the homeless.
Adelaide had a top temperature above 38C on Wednesday and the Bureau of Meteorology said the city could expect tops of 41C on both Thursday and Friday.
The Country Fire Service declared extreme conditions in two SA districts for Thursday with seven more considered extreme.
The CFS also battled three small scrub and grass fires on Wednesday but none caused major issues.
The Bureau of Meteorology said the string of hot days was the result of a very hot air mass being dragged down from central Australia.
In response, the Australian Energy Market Operator (AEMO) issued a lack of reserve notice for a short period on Thursday afternoon.
It expects the electricity reserve - the amount above forecast demand - will be 575 megawatts, below the 600 megawatts of contingency power the operator requires.
But Energy Minister Tom Koutsantonis said the state was well prepared.
"You'd have to lose, through unforeseen circumstances, 600 megawatts of generation - that is something blows up, transmission lines fall over - for there to be some kick-in of any load shedding," he said.
"In terms of the capacity of supply, we'll be fine."
The hot conditions were also taking a toll on some of the world's best cyclists in the Tour Down Under.
Wednesday's stage two went ahead as planned with the riders negotiating 148km through the Adelaide Hills.
There was no immediate word on whether organisers will opt for shorter races over the next two days.
However, the CFS said international visitors in Adelaide for the race should be aware of the increased fire danger.
The extreme heat has also prompted the state government to declare a code red which releases more funds to help the homeless with shelter, food, water, sun protection and welfare checks.
"I urge anyone who is sleeping rough to take advantage of these extra services, keep out of the heat and stay cool," Communities Minister Zoe Bettison said.
