Brace yourselves Australia: there is yet another heatwave on the way. If you were beginning to think this summer was over, think again.

A pool of heat that has been brewing over inland Western Australia is about to make its way south and east as a lingering high pressure system slowly makes its way across the south of the country this week.

By mid-week heatwave conditions are expected to reach from coast to coast, with severe heatwave conditions for South Australia.

By the end of the week the heat is expected to focus on the south-east and extreme heatwave conditions are expected for Canberra, eastern Victoria and south-eastern NSW, as well as eastern Tasmania.

A heatwave is defined by the Bureau of Meteorology as “three days or more of high maximum and minimum temperatures that is unusual for that location”.

Under extreme heatwave conditions, even healthy people are at risk and need to moderate their behaviour accordingly.

What’s the forecast?

In the rough order of how the heat will pass from west to east:

Much of inland Western Australia has been affected by severe heatwave conditions in the past few days. The heat will move west across the Nullarbor, while heatwave conditions are expected to remain inland of Broome for the rest of the week.

Adelaide is forecast to hit 37 degrees on Wednesday, 40 degrees on Thursday, and 39 on Friday.

Melbourne should endure the worst of the heat Friday, at 41 degrees, before possible storms and 36 degrees on Saturday.

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Canberra is expected to be above 35 degrees for the whole of the next seven-day forecast, with the heat peaking at 40 on Friday and 41 on Saturday — reaching extreme heatwave conditions for the end of the week.

It was only last week when the capital was blanketed in hail. If you kept any in the freezer, it could make for handy ice packs.

Hobart is forecast to reach a maximum of 38 degrees on Friday, with temperatures in the low 30s and high 20s in the lead-up, which constitutes an extreme heatwave for Hobart.

Most of the Tasmanian east coast is expected to experience extreme heatwave conditions for Wednesday, Thursday and Friday, with the majority of the rest of the state experiencing severe heatwave conditions.

Sydney is forecast to be relatively mild, peaking with 36 degrees on Sunday. But Penrith, just to the west, is expected to be 36 on Thursday, 40 on Friday, 44 Saturday, and 40 Sunday.

The daytime temperatures are impressive but when it comes to heatwaves it is the prolonged heat and lack of overnight relief that makes them deadly.

Adelaide is forecast to remain above 22 degree from Thursday to Saturday, with a minimum of 28 on Friday.

Canberra is forecast to remain above 22 degrees on Saturday and Sunday.

Fire danger

With the heightened temperatures, the fire danger will also be expected to rise, despite the recent rain.

It is still a long way out for a fire forecast but South Australia will be the first in the firing line after the heat makes its way across the Nullarbor.

The current forecast is for severe fire danger in the Lower Eyre Peninsula, Mount Lofty Ranges, Kangaroo Island, and the Lower South East on Friday.

Blackened desolation: Kangaroo Island after the bushfires. Photo: AAP

With neutral climate drivers in play and with more than a month of summer still to go, this is unlikely to be the last heatwave this season.

So it is time again to: Call and check in on your nan, take it easy in the sun, and keep an eye out for those around you.

–ABC