The devastating fires raging across northern NSW and southern Queensland have claimed the life of a person in a car near Glen Innes in the New England region of NSW.

The NSW Rural Fire Service made the announcement on social media on Saturday morning and are working with police.

"Firefighters have located the remains of a person in a vehicle at the Kangawalla fire, near Glen Innes.

"Two people remain unaccounted for after yesterday's bush fires," it read.

Fire crews have warned they can't rescue everyone as unprecedented blazes razed at least 100 properties in NSW and forced thousands of people to flee homes overnight in two states.

Residents were reportedly trapped in houses in NSW and there are fears for three missing people near Glenn Innes as wind changes pushed firefronts in new directions in NSW, sparking urgent evacuations in numerous towns and suburbs.

"Unfortunately, many people have called for help but due to the size and speed of the fires we couldn't get to everyone, even by road or helicopter," NSW Rural Fire Service warned in a tweet.

"If you've been affected or know someone who has, use #nswrfs."

NSW Rural Fire Service Commissioner Shane Fitzsimmons said emergency workers were facing never-before-seen circumstances.

"We are in uncharted territory … we've never seen this many fires concurrently at emergency warning level," he said.

"We can certainly see some of the aerial footage and the vision coming through which is identifying some widespread property damage and destruction right across multiple firegrounds," Mr Fitzsimmons told ABC on Friday night.

One person dead, two missing and 100 homes lost in unprecedented bushfire crisis_1
Inset: A home on fire at Bobin, a small town on the mid north coast of NSW. Photo: ABC

MidCoast Mayor David West, who lives in Brimbin, said he had never seen anything like the fire in his area.

"I'm looking at a sky that's screaming danger, that's saying 'get out of my way, I'm going to kill you'," he said.

"I know that sounds melodramatic but it's not. This is a fire that's devouring everything in its path."

Mid-Coast Council Mayor David West told the ABC 92,000 people in the major centres of Forster, Crowdy Bay and Harrington were affected.

"I'm looking out of my office window and all I see is what I'm assuming people in London saw during the Second World War — it's a horrible, horrible sight," he said.
Cool change

NSW can expect a brief reprieve in conditions as temperatures cool over the weekend, but the mercury is expected to rise significantly from Monday.

A cool change is also forecast for much of southern Queensland by Saturday morning, the Bureau of Meteorology's Jess Gardner said.

But fresh winds could make firefighting difficult, she added.

Hotter temperatures which have fanned the flames around the south of the state are expected to move further north on Saturday.
WA warnings

Meanwhile extremely hot, dry and windy conditions are expected to lash parts of Western Australia on Saturday, increasing the risk of bushfires in the state.

Northern and western parts of WA will cop the worst of the weather, with an extreme fire danger rating expected to be declared in three regions.

An extreme fire danger rating has been forecast for the central west, east Pilbara coast and west Pilbara coast regions. Under this rating, any fire that takes hold will be uncontrollable, unpredictable and fast-moving.

A severe fire danger rating – one level below extreme – is forecast for the lower west district including Perth, the west Kimberley coast, Kimberley inland, east Pilbara inland, Ashburton Island, Gascoyne Inland, the North Interior and Mortlock districts.

A bushfire was burning at a small town in WA's Wheatbelt region on Friday.

-with AAP