A prolonged and record-breaking heatwave that has been gripping parts of Queensland will end this week, as temperatures start to soar in other parts of Australia.

A high pressure system moving over southeastern Australia during the first half of this week will send a surge of cooler air from the Tasman Sea over Queensland. While the passage of the high will bring relief to Queensland, it will also cause a large mass of hot air to circulate over the rest of the country.

The heat will initially target the Northern Territory and northern and eastern parts of Western Australia as the high crosses the nation's southeast.

Temperatures will reach the mid forties over some inland areas of WA and the NT through the second half of the week. In WA, Marble Bar and Fitzroy Crossing are both forecast to reach 47 degrees on Friday and Saturday, which is a degree shy of Marble Bar's December record.

In the NT, Darwin is experiencing a run of oppressive nighttime temperatures as the hot air mass combines with moisture-laden air. The temperature at Darwin Airport lingered around 29-30 degrees during Monday night. With the relative humidity hanging near 80 per cent, it felt like 34-35 degrees all night. Tuesday morning's minimum temperature of 28.8 degrees was only 0.9 degrees below Darwin's December record from 1985.

While the heat will linger over parts of northern Australia all week, a brief pulse of hot air will sweep across southern Australia during the coming days, ahead of a cold front and low pressure trough.

Temperatures will spike in South Australia between Wednesday and Friday, with Adelaide expected to reach 33-37 degrees for each of the three days. If Adelaide reaches its forecast top of 37 degrees on Thursday it will be the city's hottest day since February.

The tongue of hot air will shift further east later in the week and pass over Tasmania, Victoria, NSW and the ACT between Thursday and the weekend.

The mercury will reach the high thirties to low forties between Thursday and Saturday in northern Victoria and southern NSW. Mildura's forecast top of 42 degrees on Friday would be its hottest day in 10 months and possibly the state's first day over 40 for the season. Melbourne's forecast 36 degrees on Friday is 12 above average for this time of year.

Canberra could hit the low to mid thirties between Friday and Sunday, more than five above average for December, while Hobart should venture into the high twenties on Thursday and Friday, close to 10 above the norm at this time of year.

The impending heat is likely to elevate fire danger ratings in a number of states and territories during the remainder of this week, particularly as wind strengthens near the cold front and trough as they move across southern Australia.