Adelaide in the grip of second heatwave, with more hot days to come

South Australia is on day two of a four-day heatwave that's likely to be felt right across the state, with temperatures to peak on Monday before a cool change.

Adelaide residents try and cool off at Glenelg Beach, with the state set to suffer through another heat wave. Source: AAP

Adelaide is in the grips of its second heatwave in as many weeks with forecasters tipping more to come this summer.

After four days with temperatures above 40C last week, the city will have the second of four similar days on Saturday.

Bureau of Meteorology state manager John Nairn says the sustained very hot conditions are unusual for December.

A house burns in the Adelaide Hills last week. South Australia has been rocked by horror bushfires this summer. Source: AAP

Mr Nairn says such heatwaves are more generally associated with January and February.

"We're actually building into the heatwave season, rather than peaking," he said.

The second stretch of scorching days also has the South Australian Ambulance Service bracing for a spike in heat-related calls.

South Australians are suffering through a second heatwave. Source: AAP

Since the beginning of last week's heatwave, paramedics have responded to 575 heat-related incidents, with 266 people taken to hospital.

Extra crews have been rostered over the next four days to cope with an increase in calls.

Adelaide is forecast to have a top temperature of 38C on both Saturday and Sunday before hitting 40C on Monday ahead of a cool change later in the day.

But in regional areas, the mercury will go higher with many centres forecast to have tops around 45C over the coming days.