Soaring temperatures and low humidity will form a “lethal” cocktail of conditions in New South Wales on Tuesday, with communities warned locals should brace for yet another day of fire threats.

On the east coast of the country, bushfires are still burning from the south coast of NSW up to the border of Queensland.

Bushfires are also threatening communities in Western Australia, while in Victoria an emergency warning in Gippsland was downgraded by Tuesday morning but locals were told to remain on alert.

The Bureau of Meteorology says “severe heatwave conditions” will build throughout the day, bringing temperatures over 40C to many regions of NSW. 

These conditions, combined with “grotty” smoke pollution, will put a lot of stress on vulnerable people in the coming days, NSW authorities have warned.

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The state’s unprecedented fire season has so far resulted in six deaths and more than 680 homes being destroyed.

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NSW Rural Fire Service commissioner Shane Fitzsimmons said fire crews have been “flogged”.

“We’re literally rotating through thousands of people every day, every week”, he told reporters on Monday.

NSW Health environmental health director Dr Richard Broome said Tuesday is likely to be “very hot and very smoky”.

“It’s going to be putting a lot of stress on vulnerable people, particularly elderly people who have existing heat and lung conditions.”

The NSW environment department says air quality will be “poor” in Sydney on Tuesday and could “cause symptoms, especially in people with heart or lung disease”.

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Mr Fitzsimmons said wind speeds on Tuesday won’t be as high as previous dangerous bushfire days, but high temperatures and low humidity would cancel this out.

Firefighting crews spent Monday evening back burning around the Gospers Mountain mega-fire on the Central Coast.

“These critical operations are being conducted to protect homes ahead of hot and windy weather forecast for tomorrow,” the RFS said on social media on Monday evening.

Former prime minister Malcolm Turnbull said Australia needed a new national approach to fighting and preventing bushfires, as well as dealing with the current bushfire crisis.

“If it isn’t a national security issue, what is? The national government has to provide leadership,” he told the ABC’s Q&A program on Monday night.

Mr Turnbull stressed the need for a national summit to brain storm new approaches to bushfire management.

“We do have to come together and recognise that this situation with fires is going to become worse.

“That is the inevitable consequence of a hotter and drier climate. That means we need stronger and more coordinated responses.”

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Premier Gladys Berejiklian said drought-stricken NSW could be in for a “horror summer”.

“(Tuesday) is a very dangerous day for NSW given the combination of very hot, windy conditions and that has been lethal in the last few months,” she told reporters on Monday.

There are almost 90 fires burning across NSW, with half of those were still out of control on Tuesday morning. 

-with AAP