A Code Red has been declared in South Australia providing extra support for the homeless as the state swelters through heatwave conditions.
The mercury climbed into the mid-40s in some regional centres on Monday and hit 40C in Adelaide with more of the same in store until at least Thursday.
The high temperatures prompted the government to declare a Code Red which unlocks extra funds to support homeless shelters.
The state government will also run a special phone service on Tuesday and Wednesday to provide welfare checks.
Human Services Minister Michelle Lensink said vulnerable members of the community were urged to register for the free service to get up to three calls a day from trained Red Cross volunteers.
The minister said increasing services for the homeless was also vital during periods of extreme heat.
"Agencies across Adelaide will extend their daytime operating hours over the next few days to ensure people sleeping rough are keeping cool and well hydrated during the extreme heat," she said.
Premier Steven Marshall urged all South Australians to take care during the very hot days and stay out of the sun as much as possible.
"These are extraordinary temperatures that are forecast this week," the premier said.
"My strong message to South Australians is to stay hydrated, stay out of the heat as much as possible and most importantly check on the vulnerable.
"Make sure you're looking after older people, they might be family members or next door neighbours, and make sure you're looking after your pets."
The hot weather is also expected to result in severe bushfire conditions across about five SA districts on Tuesday along with the closure of a number of parks and reserves in the Adelaide Hills.
While the Australian Energy Market Operator has urged power generators in SA, NSW and Victoria to review the forecast temperatures and, if necessary, update the electricity they plan to dispatch into the national grid.
Organisers of cycling's Tour Down Under have responded to the heat by cutting race distances on both Tuesday and Wednesday.
The weather will also prove testing for the Australian and Indian cricket teams when they clash in a one-dayer at Adelaide Oval on Tuesday.
The heat is forecast to continue through Thursday when Adelaide will have a forecast top of 35C before temperatures drop to the mid to high 20s on Saturday and Sunday.