Another heatwave will spread across the southern half of Australia this week, challenging records in some areas and elevating fire danger ratings in a number of states and territories.

A broad mass of hot air that originated in northwestern Australia will spread towards the nation's southeast during the coming days, along a slow-moving trough of low pressure.

Image: Forecast surface temperatures on Tuesday, January 15th according to the ACCESS-R forecast model.

The Bureau of Meteorology has forecast severe to locally extreme heatwave conditions for large areas of South Australia, Victoria, NSW and the ACT, along with parts of northern Tasmania and southern Queensland.

The highest temperatures this week will occur over inland areas, with sea breezes likely to limit heating near the coast. This means that central and coastal areas of Melbourne and Sydney might only reach the low to mid thirties during the next few days, while temperatures should reach the high thirties and low-to-mid forties across inland suburbs.

Penrith is forecast to reach or exceed 40 degree between Tuesday and Friday, possibly ending with a scorching top of 45 degrees. This would be their equal longest run of days days at or above 40 degrees since the site opened in 1995.

Canberra is expected to hit 39 degrees on Tuesday and 40-41 degrees between Wednesday and Friday. Canberra's longest run of days at or above 40 degrees was three in a row during 2009, with data available back to 1939.

This week's heat will be persistent during both days and nights, until a cool change sweeps through South Australia from Thursday, then crosses southeastern Australia on Friday and Saturday.

Adelaide should climb to the low forties on Tuesday and Wednesday and the high thirties on Thursday, before cooling down for the end of the week.

Consecutive hot days and warm nights pose a risk to the health and wellbeing of vulnerable members of the community, particularly the elderly, young children, pregnant women and people with a chronic illness. Some animals also struggle to cope during intense heatwaves.

This week's summery weather is the latest in a series of heatwaves that have affected Australia since late December.

Shortly after Christmas, Marble Bar registered its highest temperature on record when the mercury hit 49.3 degrees on December 27th. A few days later, Alice Springs experienced an unprecedented 45.6 degrees on December 29th. Amazingly, this record-breaking temperature was repeated just five days later on January 3rd.

Temperatures are likely to reach 46-47 degrees in northern Victoria, far western NSW and some inland areas of South Australia during the next few days. Mildura's forecast tops of 46 degrees on Tuesday and Wednesday is close to Victoria's January record of 47.2 degrees, which also occured in Mildura during 1939.

Another notable observation was a minimum temperature of 34.6 degrees at Borrona Downs - located in far northwest NSW between Tibooburra and Wanaaring - on Monday morning, December 14th. This was a new high minimum temperature record for NSW.

This weeks intense heat will also elevate the risk of bushfires. Total fire bans have been declared for all of Victoria and parts of South Australia and NSW on Tuesday. Visit each state or territory's fire service website for the latest information on fire danger ratings and alerts.