Australia heatwave
© Earth Observatory/AAPSatellite data showing the extent of the last heatwave.
A catastrophic fire danger warning has been issued as parts of South Australia, Victoria and New South Wales face another heatwave with temperatures set to hit 45 degrees in some areas.

By Tuesday, the area around the Victoria-NSW border will be experiencing a "severe" heatwave, according the the Bureau of Meteorology's new pilot program tracking the progress of heatwaves.

That area will expand across much of the inland border area and to inland Western Australia by Friday.

Forecasted strong winds in parts of South Australia have prompted the country fire service to issue a catastrophic fire danger warning on Tuesday for the lower south-east.

The fire danger is expected to be extreme in the eastern Eyre peninsula, lower Eyre peninsula, Mount Lofty ranges, Yorke peninsula, Murraylands and upper south-east regions, and severe in north-west pastoral, north-east pastoral, west coast, Flinders, mid-north, Adelaide metropolitan, Kangaroo Island and Riverland regions.

The new catastrophic warning level was brought in after the devastating Black Saturday bushfires in Victoria in 2009 and comes as temperatures are forecast to reach 45C in parts of the state.

The CFS advises people in bushfire-prone areas to leave the night before or early in the day in the case of catastrophic fire danger.

"If a fire starts and takes hold, it will be extremely difficult to control and will take significant firefighting resources and cooler conditions to bring it under control," it says, adding: "Homes are not designed or constructed to withstand fires in these conditions."

Adelaide will experience maximum temperatures of between 33 on Tuesday and 41 on Thursday - a repeat of Monday's high.

Melbourne reached a top of 39C on Monday, but a cool change will bring shortlived relief with a 25C maximum temperature on Tuesday before increasing to 39C on Friday. Coastal regions will be helped by cool winds.

The south-west of NSW will experience temperatures in the low 40s for most of the week.

Extreme fire danger is also forecast for the Victorian regions of Wimmera and the south-west and there will be a total fire ban in place for south-west, north central, Mallee, northern country, Wimmera, east Gippsland, north-east, central west and south Gippsland regions owing to the high temperatures and strong winds.

"The total fire ban is in place to minimise the chance of fire starting," said the country fire authority state duty officer, Stephen Walls.

"The fire services are doing their part to be prepared for tomorrow and we need the community to help by taking care not to do anything that may cause fires.

"People also need to be aware of what is happening in their local area and stay informed."

It is the second heatwave this month after record temperatures added to what the Bureau of Meteorology described as "one of the most significant multi-day heatwaves on record".

A report released by the bureau last week said the heatwave was notable "for its duration".

"Although peak temperatures generally fell short of those experienced during the 2009 heatwave, it lasted for longer in some locations, particularly near the coasts of Victoria and South Australia."