The remnants of a coast-to-coast heatwave are being swept off the NSW coast after baking Sydney and delivering a record hot night in the outback.
Sydney reached its forecast 38C by 2pm before plunging to 27C by 3pm while Gosford shed 13C in 35 minutes as a southerly change began paving the way for a cooler weekend.
The mercury in large swathes of NSW had earlier exceeded 42C including Newcastle Airport, Coonamble, Bourke and, topping 43.9C, the outback village of Girilambone.
Inland South Australia and southwest Queensland are also experiencing another hot day but not quite a repeat of Thursday's mid to high 40s.
Birdsville, on the edge of the Simpson Desert, followed a near-record high day of 49.4C by notching the second hottest overnight temperature in Australia on record.
The temperature fell to a balmy 36.4C at 2.20am - two-tenths short of the national record - before reaching 45C on Friday.
Not that it bothered Birdsville Hotel general manager Ben Fullagar, who had not found the temperature remarkable.
With a dry heat and the dew point mostly staying below 20C, it felt like a normal day, he told AAP.
"Everyone was just mowing lawns and council was doing works (on Thursday)," he said.
"I took the dog for a walk last night about 10pm and it was warm ... but most of our properties will hold 24C inside."
The biggest concern, he said, was a loss of power but he hadn't noticed any hiccups from the town's diesel generators.
The overnight low, dipping fractionally below the 2019 mark set at NSW cattle station Borrona Downs, came hours after Birdsville fell a tenth of a degree short of the Queensland temperature record of 49.5C.
Country music fans did not let the rising mercury evaporate their enjoyment of Australia Day at the Tamworth Country Music Festival as temperatures topped 38C.
Lenore Klumpp and Janelle Pollack huddled under a shade cloth in the morning cooking up plans to spend the day in the pub.
"We'll be having a drink, having a dance," Ms Pollack said.
"But more dancing than drinking."
Much of SA is about 10C cooler, with Adelaide enjoying a 24-degree maximum.
Heatwave conditions continue in parts of Queensland's west and interior but are cooler on the coast.
Brisbane fell a few degrees short of a forecast 33C while the Gold Coast hovered about 30C.
The southerly change spreading across the southern and eastern states will lower temperatures noticeably by late Friday.
