A Code Red has been declared in South Australia as temperatures are expected to climb up to 48C.

Adelaide and much of the state will continue to endure heatwave conditions, with authorities warning the soaring temperatures could pose a risk to anyone who does not take action to keep cool.

The State Emergency Service has issued an extreme heatwave emergency warning and the state government has declared a Code Red for Tuesday and Wednesday as temperatures soar towards the high 40s in some parts of the state.

The Code Red triggers extra funding so services for the homeless can be extended while a special phone line will also operate for the next two days, providing regular checks on the elderly and others at risk from the extreme conditions.

Adelaide is forecast to have a maximum temperature of 41C on Tuesday and 40C on Wednesday before cooler conditions push through the state on Thursday afternoon.

The top in the city on Monday also hit 40C while in northern centres like Marree it climbed to 48C.

Premier Steven Marshall has 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.”

The SES said the extreme conditions, with little relief even at night, would pose a particular risk to babies and young children, the elderly, pregnant women and those who are already unwell.

“But in an extreme heatwave, even healthy people who do not take action to keep cool can become very ill,” the service said.

‘Only going to get worse’

Amid the searing conditions, the Australia Institute is set to release a report on Tuesday that suggests Adelaide could experience nearly three times as many days over 35C by 2090 unless action is taken to better tackle climate change.

The report, from the institute’s Climate and Energy Program, uses CSIRO and Bureau of Meteorology modelling to show how areas in and around Adelaide will get hotter more regularly.

“Adelaide already has some of the hottest weather of any Australian capital city and, unless we do more to tackle dangerous global warming, that is only going to get worse,” the institute’s projects manager Noah Schultz-Byard said.

Australia prepares to swelter

The hot weather comes as the Tour Down Under cycling event gets ready to kick off in Adelaide on Tuesday and the Australian Open fires up in Melbourne.

Tennis players will have cooler conditions than the cyclists but only just.

Melbourne is forecast to experience temperatures in the low to medium 30s all week.

An extreme heatwave is expected to sizzle across most of eastern NSW this week while the rest of the state will experience severe conditions.

Sydney temperatures are expected to be above 30C through to the weekend while the west suburbs could top 40C with Penrith forecast to reach 45C on Friday.

Records have already started breaking with Borrona Downs in the state’s northwest recording the highest minimum temperature ever in NSW with 34.6C on Monday.

The heat combined with thunderstorms and increased winds will result in severe bushfire danger.

In Queensland’s Central West, Barcaldine will reach 41C on Tuesday while Brisbane will average in the low 30s for the rest of week.

The west coast won’t be spared the high temperatures either with Perth set to reach 38C on Saturday and 40C on Sunday.

In the Northern Territory, storms are forecast in Darwin throughout the week with temperatures around 33C.

Residents of Tasmania can expect cooler conditions with Hobart’s highest temperature over the next week 29C. with light showers on Thursday and Friday.

With AAP