It is the heatwave that laps east and west and seems hard to dislodge.
Even tropical cyclone Narelle, wandering off the north-west coast of Western Australia, has so far failed to budge the giant heat cell over the continent.
"The system is holding its shape," said the manager of climate monitoring at the weather bureau, Karl Braganza. "You are still getting the hot core over the inland."
But the core is stretching eastward again, sending the mercury higher for populated regions ranging from Victoria to Queensland. Brisbane had its hottest night in seven years, with the temperature dropping to 25.8 degrees but the city "was very humid so it felt more than that", said Weatherzone meteorologist Melissa MacKellar.
Sea breezes are forecast to keep the temperatures in Sydney around the harbour to peaks of 30 and 34 degrees on Friday and Saturday, according to the latest forecasts. But move only about 25 kilometres west to Bankstown, and days of 41 and 39 await.
Melbourne can expect 37 on Friday before a cool change arrives and keeps temperatures down for a week. Most other parts of Australia won't get much relief.
"Our models are showing the high pressure system dominating weather over southern and south-eastern regions of Australia for the next week," said Ms MacKellar.
NSW, the ACT and Victoria have declared total fire bans for today, while early rain is likely to ease fire conditions in parts of Tasmania. For mainland regions, the latest heatwave may be less threatening than earlier in the week.
''Winds are not expected to be as strong as last Tuesday's,'' said Julie Evans, a senior meteorologist at the bureau.
Records, meanwhile, continue to fall. Leonora in central WA claimed the temperature peak for the fortnight-long heatwave, notching 49 degrees on Wednesday. The remote town had broken its previous record just a day earlier at 48.3. The 47.8 level reached on Monday matched a high that had stood for about 55 years.
Inland regions of NSW, such as Tibooburra, will come close to those levels, with 48 predicted for Sunday. Victorian towns such as Mildura and Swan Hill, meanwhile, may see peaks of 42 during the next ramp-up on Friday.
Weatherzone, owned by Fairfax Media, predicts several towns from Birdsville to Moomba will come close to 50 degrees in coming days.
This week the bureau drew international attention after it added extra colour to its forecast charts to extend the range to 54 degrees. Temperatures in the 50-52 will be shown as a deep purple while regions will be marked a bright pink should they land in the unprecedented 52-54 range.
"One big question is what's going to happen to the monsoonal trough," said Aaron Coutts-Smith, NSW manager of climate services at the bureau. "It's been a relatively late start to the monsoon."
The weak monsoonal conditions mean northern regions aren't getting the cloud cover and rainfall that would normally sap some of the heat collecting in the interior.
"That can really put a lid on extreme temperatures," he said.
Average or below-average temperatures on Wednesday across much of Victoria, Tasmania and parts of NSW saw the run of exceptionally hot average national maximums end. Wednesday's average maximum came in at 38.36 degrees.
The first eight days of 2013 made it into the top 20 hottest days for Australia in more than a century in terms of the average maximum temperature. The mean temperatures - averaging maximums and minimums - smashed the previous record on Monday and then again on Tuesday.
The mean of 32.32 degrees on Tuesday was almost half a degree higher than the record that had stood for more than 40 years until this week.