Fire crews brace as bushfire emergency continues across Vic, NSW and SA_1

A police forensic team is on its way to South Australia's Kangaroo Island after two people were confirmed dead and fire crews continue to battle out-of-control bushfires across the island.

The latest tragedy comes as two Victorians were killed in the East Gippsland fire zone and another 21 people are still missing with seven emergency warnings issued as of 12pm on Saturday.

The deaths take the national bushfire death toll to 23 and are an ominous sign for NSW and Victoria bracing for a "fire onslaught" with terrifying conditions forecast for Saturday.

Wind gusts of almost 70km/h have already been recorded in Victoria's Mt Hotham region and will continue to increase throughout the day, authorities warn.

Thousands of people remain in fire danger zones as Alpine Shire Mayor Peter Roper warned a southerly wind change later on Saturday could impact more remote communities including Dinner Plain, Falls Creek and north of Mt Buller.

In NSW, tens of thousands continue to flee the south coast as the death toll there stands at 17.

Premier Gladys Berejiklian urged people to evacuate bushfire hotspots while they still had time, but authorities have warned the window to leave is closing.

"All of the major road networks are still open, but we can't guarantee that beyond the next few hours. So, there are still windows for people to get out," she told reporters on Saturday.

More than 3000 firefighters are on the frontline, with 31 specialist strike teams in place across NSW as firefighters warn some towns cannot be defended.

NSW Rural Fire Service Commissioner Shane Fitzsimmons said temperatures would soar past 40 degrees in NSW before a "volatile" southerly wind sweeps through on Saturday afternoon.

Victorian death toll remains at two, with 21 missing

Twenty-one people are still missing in Victoria's deadly bushfires raging in the state's east that have already killed two men.

The number of missing people is expected to fluctuate, Chief Commissioner Graham Ashton says.

Authorities are trying to get into 18 isolated communities in East Gippsland and the northeast where fires have been raging all week, but so far access has only been achieved at two.

Many fires in East Gippsalnd have already merged and the current risk is the 124,000-hectare fire in the northeast at Corryong merges with another fire in NSW.

Fires and evacuation orders are also in place across Victoria's Alpine region.

The wind change has already moved through Melbourne and was due to hit East Sale at 10am, Wangaratta about 1pm and Albury at 4pm.

"We have a long way to go today. Today is a very challenging day for all of us," Mr Crisp said.

-with AAP