Every state and territory, at least in part, is likely to face a heatwave in the coming days as scorching late summer weather bakes the country.

A break in the monsoon has allowed sweltering air to build up in the Pilbara which is heading across Western Australia and the Northern Territory to the nation’s east with major cities in its sights.

“For Melbourne and also Penrith, it’s likely to be the hottest weather we’ve seen so far this summer as this heat slides on through,” said Sky News Weather meteorologist Rob Sharpe.

That could mean the mercury surpassing 40C in parts of New South Wales, Queensland and Victoria on the weekend. Or even 50C in the Pilbara itself.

Hobart and Canberra could also see heatwave conditions and Adelaide won’t be far off

And forecasters have warned, that although there could be a slight cool change to round out the weekend, the blistering heat may ramp up again early next week.

The Bureau of Meteorology (BOM) has warned Thursday to Monday could see the most widespread heatwaves across Australia.

It defines a heatwave as three days when the maximum and the minimum temperatures are “unusually hot”.

A severe to extreme heatwave will cover much of WA but should bypass Perth and the southwest.

50C plus possible in WA

Broome is expected to see between 34-35C every day for the next week. Website Weatherzone said a 50C temperature could be reached on Friday or Saturday in the Pilbara. In February, this has only been recorded once before when Mardie, 135km south of Karratha, reached 50.5C in 1998.

It will be sunny in Perth with a high of 26C on Thursday rising to 33C on Saturday and 34C on Sunday. Minimums in the mid-teens but as high as 20C on Monday morning.

A low intensity heatwave, with patches of severe heatwave, will then funnel through central SA and into the eastern states.

Adelaide could hit 38C on Thursday as that ribbon of heatwave passes north of the city. It should then cool on Friday and Saturday to the mid-twenties with 19C lows before rising again to 29C on Sunday and then as much as 35C next Wednesday.

Melbourne could nudge 40C

On both Thursday and Friday it’s likely to hit 35C in Melbourne with a low of 24C. There could be a thunderstorm on Friday.

But Sharpe has said that could be an underestimate.

“I actually think we’re going to be hitting the high 30s in Melbourne which is well above the bureau’s forecast”.

For Saturday it should go down to just 22C and then 26C on Sunday.

Mildura could get up to 43C on Friday before dropping 10C on Saturday, while Yarrawonga is forecast to get to 41C on Friday.

All of Tasmania could see a low intensity heatwave From Wednesday until Friday with the conditions in Hobart continuing into the weekend.

Temperatures in the city are looking at 28-29C for Thursday and Friday before dropping to 24C on Saturday and then up again to 27C on Sunday. Minimums will be in the mid-teens. There could be a shower or two on Sunday.

Launceston should get as high as 33C on Friday.

Canberra is forecast to have 30C plus days until Wednesday. A high of 31C on Thursday will creep up to 33C on Friday and then 34C on Saturday accompanied by a possible storm. Overnight lows should be 14C early on Friday and 16C first thing Saturday.

39C in parts of Sydney

Coastal winds should moderate the heatwave in Sydney’s CBD but Saturday could still reach 32C. Expect just below 30C to end the week with 20C at dawn. A thunderstorm is possible on Saturday ahead of the slight dip in temperature.

But the cooler maximums won’t get very far inland. Penrith, in the city’s west, will be uncomfortably hot for the next week. Thursday’s high of 33C will jump to 39C on Saturday. A drop to 31C on Sunday will lead into a 37C Monday.

The heatwave will spread across much of coastal southern NSW and northern NSW. Nowra will go from 31C on Thursday to 36C on Sunday, Tamworth will peak at 38C from Saturday to Tuesday and Bourke is facing a 42C Saturday.

Huge amounts of rain in northern Queensland

In Queensland, heatwave conditions will persist across southern border areas from Thursday into next week. Thargomindah is in a pattern of at least 40C days touching 43C on Monday.

Brisbane isn’t in the heatwave zone but will see a string of warm days nonetheless. For Queensland’s capital it’s likely to be rinse and repeat weather for the coming week. Partly cloudy days will get to 30-31C with nights around 19-21C. No rain is in the forecast.

But rain is very much in the forecast for northern Queensland.

Cairns could see huge downfalls with 70-200mm possible on Thursday and up to 150mm on Friday and then lesser, but still hefty, falls over the weekend.

A tropical low is bouncing around the Gulf of Carpentaria which will deliver heavy falls for Burketown, Cooktown and Weipa.

Mostly dry in Darwin for the end of the week although afternoon thunderstorms could bring a few patches of rain. Temperatures will top out at 33C with 27C lows. Stormier weather could be in store for the Top End over the weekend.

- Benedict Brook, news.com.au