A heatwave persists for large swathes of the nation with a cool change not expected to bring relief until later in the week.
Severe to locally extreme heatwave conditions extend through northern parts of South Australia, much of southwest Queensland and into northern and eastern NSW.
A wave of hot air swept across inland Australia, southeast and southwest Queensland and most parts of NSW.
Queensland's Birdsville on the SA border hit a sweltering 47.9C on Wednesday and Smithville in NSW clocked up 46.4C.
The remote outback town of Oodnadatta, home of Australia's equal hottest temperature at 50.7C recorded in January 1960, climbed to 47.5C just after 2.30pm.
Severe heatwave conditions across the central and northern inland parts of NSW spread east towards Sydney, the Hunter and mid-north coast on Wednesday.
Some regions in the northwest slopes and plains, such as Walgett, reached 40.4C, while parts of upper-western NSW, including Fowlers Gap and Borrona Downs hovered just above 44C during the afternoon.
The heat won't be over yet with the Bureau of Meteorology forecasting both maximum and minimum temperatures in heatwave-affected areas to be 5C to 10C above average throughout the rest of the week.
Temperatures in NSW are expected to reach their highest on Thursday and Friday, coinciding with elevated fire conditions towards the end of the week.
Bureau senior meteorologist Dean Narramore said the very hot air from inland areas - some of which could experience temperatures as high as 48C during the week - would reach eastern parts of NSW by Friday.
At the Little Topar Roadhouse, about 80km northeast of the NSW outback town of Broken Hill, owners Jo Lindsay and Kim Starkey were getting ready to bathe their 17-month-old macaw Charlie Girl in the stifling heat.
The pair were largely without customers due to a lack of people stopping for a bite as the temperature soared towards the mid-40s.
"We're just keeping cool and entertaining ourselves with birds," Mr Starkey told AAP.
NSW Health executive director Jeremy McAnulty advised people to look out for vulnerable members of the community.
"Heat can kill people, it can make people with underlying health conditions tip over into a much worse condition," he told reporters in Sydney on Wednesday.
Severe heatwave conditions also blanketed South Australia's northwest, northeast and Flinders regions, with some areas reaching the high-40s.
The remote outback town of Oodnadatta, home of Australia's equal hottest temp at 50.7C recorded in January 1960, climbed to 47.5C just after 2.30pm.
It was a noticeably cooler day for the southern state's capital, recording 29.5C, a welcome relief to the 41C recorded on Tuesday.
Mr Narramore said it will be a very hot next few days but a cool change will move in by the weekend.
"As we get to Thursday and Friday, we're going to see temperatures in northern South Australia, southwest Queensland and northern NSW in the mid to high 40s," he said.
"Thankfully a cool change will move into southeastern parts of the country by Friday then sweep through NSW on Friday night and Saturday, dropping temperatures back to average or even slightly below for the weekend," he added.
Emergency services have urged people to watch out for signs of heat stroke or heat exhaustion.
Extreme fire dangers were also in place for parts of the Pilbara coast.
