A weak cool change is beginning to move up the NSW coast after the state sweltered through the peak of a record-breaking heatwave but forecasters say any relief will be short-lived.
Temperatures soared past 46C in the northwest on Friday as scorching conditions continued to break records ahead of the milder weather.
A small patch of rural NSW endured the hottest night ever recorded in Australia, with a minimum overnight temperature of 35.9C halfway between Cobar and Wilcannia, at Noona.
"That's an all time Australian record for the warmest night at any time of the year," the Bureau of Meteorology's Ann Farrell told reporters in Sydney.
Just over an hour away from the tiny community, locals at Cobar said the heat was taking a toll on workers, and power bills, as people struggled to keep cool.
A kitchen thermometer at Cobar's Empire Hotel had repeatedly reached 50C, bar attendant Britney-Lee Fazulla told AAP.
"It's very difficult but we push through," she said.
The 19-year-old, who has lived in Cobar all her life, said it was the worst heatwave she's experienced.
The central western town also recorded its highest ever minimum temperature overnight of 33.2C.
At Tibooburra Airport the mercury climbed to 46.9C, while in the ACT Canberra experienced its fourth day in a row above 40C for the first time since records began.
In Sydney, Penrith reached 42.1C while an earlier than expected sea breeze capped temperatures in the CBD at 29.5C.
The conditions made it tough going for firefighters, the NSW Rural Fire Service tweeted, with 78 bush and grass fires - 40 of them uncontained - burning as of 5pm.
While temperatures in some areas are expected to drop by 10C, only a one- or two-degree difference will be felt further north by Sunday.
Health authorities are urging people to take extra care and keep hydrated during the heat. (AAP)
"The most marked difference will be along the coast but inland parts will see some relief," duty forecaster David Wilke told AAP on Friday night.
He and Ms Farrell both said any relief would be temporary, with temperatures expected to gradually start heating up again.
"It looks like into late next week we're sort of almost back where we were today," Mr Wilke said.
Heart Foundation NSW chief executive Kerry Doyle reiterated that people should take extra care and keep hydrated, especially the elderly, children and those with heart issues.
