Challenging conditions are being experienced across NSW, with extreme fire danger warnings in place in many areas.
Total fire bans have been issued for Sydney, the Hunter and Illawarra regions and on the far south coast, close to where thousands of hectares have been burnt out across the River Murray in Victoria.
A sweltering 43C forecast is in place for Sydney and even higher in its western suburbs.
Central and western NSW are also baking, with Bourke forecast to reach 42C and Dubbo 40C.
Temperatures in Canberra are expected to hit 37C.
The Bureau of Meteorology says damaging winds are likely to develop over parts of southeastern NSW on Saturday. Â
West to northwesterly winds will then strengthen ahead of a trough that will move through the region on Sunday.
"We enter today with very challenging weather conditions right across the state," Rural Fire Service Commissioner Trent Curtin told reporters in Sydney.
"We have high fire danger predicted across most of the state ... with many areas predicted to have extreme fire danger conditions."
There are 44 fires burning in NSW - four of them uncontained but none of serious concern.
"We enter today in good condition," Mr Curtin said,
"We're ready to fight bushfires that might start throughout the day."
Volunteers are at the ready across the state, with 600 back-up firefighters also available at 20 minutes' notice.
Some 50 aircraft can be rapidly deployed, including four heavy helicopters and three large air tankers, Mr Curtin said.
NSW Premier Chris Minns said Saturday would also be "incredibly challenging" for health workers.
"Look after one another ... particularly the old and young," he said.
"Look after your pets. We lose people on the incredibly hot days. People die as a result of extreme heat in Australia. That is the truth."
Ambulance Commissioner Dominic Morgan said the service was anticipating a 10 per cent jump in call numbers due to the extreme weather.
Victorian cities and towns will eventually be able to look forward to a reprieve as temperatures drop on Saturday.
After climbing to 43C on Friday, Melbourne was in for a considerably milder top of 27C on Saturday.
The southwest was expected to be cool to mild with possible late showers, and the southeast windy and warm.
The state is not yet clear of fire danger as the combination of an arid landscape, dry lighting and erratic winds could ignite blazes.
The strong southwesterly change has also prompted warnings for damaging winds up to 90km/h from the South Australian interior to eastern Victoria.
NSW centres including Sydney are also awaiting a cooler change to sweep the state late Saturday evening.
15°C