Cities, regions on alert ahead of Christmas fire threat

Millions of residents and travellers are being warned to stay alert as the risk of Christmas week infernos intensifies.

Several states entered Monday battling dangerous blazes or warning of potential outbreaks, including NSW, with hot, dry and windy conditions expected to pose extreme fire danger in Sydney.

The Hunter and other northern parts of NSW also face extreme conditions and total fire bans.

Meanwhile, Victorian and South Australian authorities are preparing for catastrophic and extreme conditions on Boxing Day.

"Boxing Day is a big travel day right across the state, so we urge those travelling to download the VicEmergency App before you go," Victorian Country Fire Authority deputy chief officer Garry Cook said on Sunday.

Towns and tourism providers were already nervous in Victoria as a massive bushfire cut through the state's west at the weekend.

The Grampians National Park blaze had burned through more than 36,000 hectares - about 20 per cent of the park's footprint - and forced several villages to evacuate before pivoting northeast late on Sunday.

Halls Gap Hotel shut its doors, tourism providers were reportedly losing $1.9 million a day in bookings and family celebrations were in strife as residents fled to Ararat.

"With 39-degree days Xmas and Boxing Day, we've cancelled our family Xmas here this year," Moyston resident Maxine Windram said on social media.

Fire conditions are expected to ease across Victoria in the coming days before catastrophic conditions in the Wimmera and extreme danger in most other districts, including Melbourne, on Boxing Day.

Regional areas of South Australia are also expecting similar conditions the day after Christmas.

Firefighters were mopping up a blaze on Sunday that had threatened life and property on Perth's northern outskirts.

The fast-moving fire at Two Rocks forced evacuation warnings on Sunday afternoon but was later brought under control.

High fire danger is again forecast for the region on Monday while extreme risk is predicted in inland parts of Western Australia's midwest and southwest.