A blast of hot weather across Australia's southeast has left Sydney, Canberra, Adelaide and Melbourne all sweltering together for the first time in more than half a century.
Temperatures peaked above 33C in all four capital cities on Tuesday - the first time that's happened in December since 1965, according to the Bureau of Meteorology.
Hot, dry winds drawn down from northern Australia drove the mercury higher, sparking fire bans in NSW, South Australia and Victoria.
Sydney's CBD sizzled at a high of 37.8C - nearly 13 degrees above the city's long-term average for December - while at Penrith, in the city's west, the mercury surged to 39.4C.
About 800 people had flocked to the Aquatic Centre at Sydney Olympic Park in the city's west before lunchtime to seek relief from the city's hottest December day since 2005.
"That is higher than normal, particularly for a Tuesday and given it is a work day," a spokesman said, adding that crowds were expected to double.
In Melbourne, temperatures leapt above the forecast maximum of 34C to reach 36.1C shortly after 4pm.
Adelaide was a touch hotter at 35.6C, while Canberra hit 33.9C.
Cool winds were expected to bring relief tonight for Melbourne and Adelaide, but Sydney and Canberra face another hot one on Wednesday.
Sydney's overnight temperatures are expected to remain at a sticky 26C, not far off the record of 26.3C set in December 1972.
By 9am on Wednesday, temperatures are expected to be well into the 30s and peak shortly after at 38C.
The bureau's senior forecaster Neale Fraser said a southerly change should cool things down late in the afternoon.
"That will bring a dramatic drop in the temperature," he said.
"There also may be some late showers as well. But before then a hot night and another hot day."
To help cope with the hot weather, the Red Cross is urging people to keep an eye on their neighbours.
"Older people, pregnant women, children, those with a disability and people taking medications are among those who are more at risk," a spokeswoman said.
St Vincent's Hospital and workers from the City of Sydney council have been busy providing homeless people with water, sunscreen and details about where to seek shade.
Meanwhile, more than 45 fires were burning across NSW on Tuesday, including two large blazes which threatened dozens of homes near the towns of Abermain and neighbouring Neath, near Cessnock in the Hunter region.
At least 70 firefighters were on the ground while water bombing helicopters helped from above.
With hot and windy conditions forecast to continue, total fire bans have been declared for the greater Sydney region, Illawarra/Shoalhaven, Upper Central West Plains and Lower Central West Plains on Wednesday.
However, fire bans that were in place across northern Victoria and most of South Australia are expected to be lifted.
The SA Country Fire Service said that the threat posed by a fire on 3300 hectares of land near the Nullarbor Roadhouse on the Eyre Highway had reduced.
