The men, aged 63 and 29, died trying to defend their home as an out-of-control blaze swept through Cobargo, on the NSW south coast, where dozens of homes and outbuildings have been destroyed.

Their deaths take the national bushfire toll to 13, after volunteer firefighter Samuel McPaul, 28, died when his truck flipped amid a "fire tornado" at Jingellic in NSW, near Albury, on Monday night.

"Absolutely, this has to be one of the worst, if not the worst fire season we have experienced," NSW Fire Commissioner Shane Fitzsimmons told reporters on Tuesday.

More than 100 fires continue to burn in NSW, where more than 900 homes have been destroyed this bushfire season, over 3.6 million hectares of land has been razed and an elderly man is missing.

"We are absolutely stretched right across New South Wales. We have fires burning from the Queensland border all the way down to the Victorian border across the Great Dividing Range," Mr Fitzsimmons said.

"It's been a truly awful day."

In Victoria, 33 major fires continue to burn, four people are missing and thousands of homes have lost power as the Defence Force moves in to help evacuate people.

Multiple emergency warnings remain in place across East Gippsland, where fires have ripped through more than 230,000 hectares and dozens of homes are expected to be destroyed.

Black Hawk helicopters, fixed-wing aircraft and naval vessels, including the HMAS Choules and the MV Sycamore, have been deployed, along with military personnel.

The news comes after the Emergency Management Commissioner Andrew Crisp warned the fire risk remained "dynamic".

Despite this, there was some "relatively good news" as a wind change pushed the worst of the fires passed the small community of Mallacoota, where 4000 people were forced to shelter on the beach earlier in the day.

Conditions will continue to challenge firefighters further north, however, as a wind change rips up the NSW coast.

"It will be cooler but they're strong and gusty south to southwesterly winds that will lead to a change in the direction the fires are moving," meteorologist Dean Narramore told AAP.

"It'll expand the fire area, so you're going to have new challenges, new problems and new areas impacted."

Warning levels for a string of bushfires burning on the South Australian mainland have all been reduced but concerns remain for six blazes, including those burning on Kangaroo Island and near Whyalla.

In southern Western Australia, a large bushfire continues to rage in the Stirling Range National Park, as more than 40 bushfires burn across the state.

One home has been destroyed in Tasmania, where more than 30 bushfires continue to burn, six of concern.

Australian Associated Press