Warnings were issued in NSW, Queensland and the ACT, with an extreme heatwave declared for Australia's far-north tip on Tuesday as temperatures were expected to hit the high 30s.
Inner Sydney reached the low 30s while Camden and Penrith almost broke into the 40s, topping out at 39.7C on Tuesday afternoon.
The Bureau of Meteorology issued severe heatwave warnings for large swathes of the NSW coast, including the Sydney metropolitan area, the Hunter region and the south coast.
The temperatures are well above spring norms, with Richmond hitting 12C above its average November maximum temperature of 27C.
Bureau senior meteorologist Jonathan How said those areas were set to be blasted with even more historic heat on Wednesday.
"40C tomorrow in Penrith and Richmond, the last time it was this hot in November was back in 2020, so four years since we've had temperatures this high," he told AAP.
"Particularly through western Sydney, one of the other reasons we're seeing heat recognition is because night-time temperatures are also quite high, overnight minimums remaining above 20C across the city over the next two nights."
The energy regulator has warned there is a risk of power shortages as temperatures soar. (Bianca De Marchi/AAP PHOTOS)
Sydney's city centre is forecast to reach a predicted maximum of 33C on Wednesday.
Many remote areas north of Cairns have been hit with heatwave warnings and Mr How said there was no respite in sight.
"Even two to four degrees above average in those areas has temperatures pushing into the 30s, so hot days and hot nights and really no relief on the way," he said.
Temperatures in Canberra reached a peak of 32C on Tuesday.
Planned outages at a number of coal-fired power plants in NSW also placed stress on the grid as people rely on air conditioners to help them beat the heat.
But the Australian Energy Market Operator (AEMO) lifted a warning of potential blackouts, although risks of low energy reserves remained.
The regulator said NSW would have the requisite electricity supply to get through Tuesday, although there was still a chance of shortages later in the week.
The Bureau of Meteorology has warned severe heatwaves can be dangerous for many people. (Bianca De Marchi/AAP PHOTOS)
"Ongoing heatwave conditions combined with significant generation outages in NSW tomorrow and Thursday remain a risk," a spokeswoman said.
"AEMO is actively managing the situation and has issued updated Lack of Reserve (LOR) notices, urging industry participants to respond to projected demand requirements in the coming days."
The bureau warned severe heatwaves can be dangerous for many people, including pregnant and breast-feeding women, babies, older people and those with medical conditions.
21°C