Australia this week experienced its hottest day on record and the heatwave is expected to worsen, exacerbating an already unprecedented bushfire season, authorities said Wednesday.

The average nationwide temperatures of 40.9 degrees Celsius (105.6 degrees Fahrenheit) on Tuesday beat the previous record of 40.3 degrees Celsius in January 2013, the Bureau of Meteorology said.

"This heat will only intensify further today," meteorologist Diana Eadie Said.

The heatwave is another alarm bell about global warming in Australia, where this year's early and intense start to regular summer bushfires has heaped pressure on the Australian government to do more to tackle climate change.

Hundreds of bushfires have been raging across Australia for months, including a "mega-blaze" burning north of Sydney, the country's biggest city.

Smoke from the fires has engulfed Sydney, raising air pollution to levels so hazardous that leading doctors have labelled the event a "public health emergency."

At least three million hectares (7.4 million acres) of land has been torched across Australia, with six people killed and about 700 homes destroyed.

Scientists say the blazes have come earlier and with more intensity than usual due to global warming and a prolonged drought that has left the land tinder dry and many towns running out of water.

The fires have sparked climate protests targeting the conservative government, which has resisted pressure to address the root causes of global warming in order to protect the country's lucrative coal export industry.