As the nation sweltered through its hottest day on record, Australia has claimed another heat-related milestone - playing home to 14 of the 15 hottest places on earth.

Data measured by El Dorado Weather and The Bureau of Meteorology suggests a village in Botswana, Africa, was the only place in the world with higher recorded temperatures on Wednesday.

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The nationally-averaged maximum daytime temperature was 41.9 °C exceeding the record set on Tuesday - 40.9 ºC.

Queensland claimed the second, third and fourth hottest places in the world at Birsdville Airport, Urandangi and Bedourie, while South Australia came in with five of the top 15.

Fitzroy Crossing, Marble Bar, Curtin and Mandora in Western Australia made the list, alongside Wulungurru and Jervois in the Northern Territory.

The hottest place in Australia

Australia’s highest temperate ever recorded was on January 2, 1960 in Oodnadatta, South Australia. On this day, the mercury hit 50.7C degrees Celsius.

This is closely followed by Mardie in Western Australia, when on February 19, 1998 the temperature reached 50.5C degrees Celsius.

World’s hottest places - December 18

Pandamatenga (Botswana) - 49°C Birdsville Airport (Queensland) - 47.7°C Urandangi Aerodrome (Queensland) - 47.5°C Bedourie (Queensland) - 47.5°C Fitzroy Crossing Aero (Western Australia) - 47.4°C Wudinna Aero (South Australia) - 47.3°C Marble Bar (Western Australia) - 47°C Curtin Aero (Western Australia) - 46.8°C Mandora (Western Australia) - 46.8°C Jervois (Northern Territory) - 46.6°C Tarcoola Aero (South Australia) - 46.6°C Ceduna Airport (South Australia) - 46.5°C Port Augusta (South Australia) - 46.4°C Wulungurru (Northern Territory) - 46.4°C Marree Aero (South Australia) - 46.3°C

Records tumble

A town in South Australia’s west has recorded the state’s hottest-ever December day, as it swelters through a four-day heatwave.

Nullarbor broke the record when it hit 49.2°C on Thursday afternoon.

Adelaide could also be set for its hottest December day, with an upgraded forecast high of 46°C predicted for Friday.

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South Australian firefighters are on edge ahead of Friday’s scorcher, with extreme temperatures set to be accompanied by damaging winds and thunderstorms over large areas of the state.

Winds could be so strong water bombers and support aircraft could be grounded.

State of Emergency

Several firefighters have been injured and dozens of homes are feared to have been lost as bushfires burn out of control in New South Wales.

Two bushfires have been escalated to emergency level, with almost 100 burning elsewhere.

A fire burning out of control in Green Wattle Creek, southwest of Sydney, is one of two fires at emergency warning level on Thursday afternoon.

Flames are seen during a bushfire near Bilpin, 90km north-west of Sydney. Credit: MICK TSIKAS / AAPIMAGE

It is feared at least 40 homes and structures have been destroyed by the blaze.

Three firefighters are also being treated for burns sustained while battling the fire.

- With AAP

The Latest from 7NEWS will be LIVE with every development on the NSW bushfire crisis immediately after the cricket on Thursday night