Several states face growing bushfire risks from Boxing Day as temperatures are set to suddenly soar.

Victoria has been warned it faces its worst conditions since the Black Summer bushfires of 2020, as out-of-control blazes continue to rage across the state.

A fire in the Grampians, in the state’s west, has already burnt more than 41,000 hectares and there are fires in Bullengarook in Melbourne’s northwest, and the Gurdies in western Gippsland.

But conditions are set to intensify across the state when temperatures reach into 40C on Boxing Day, fanned by strong and dry winds, Victorian Emergency Management Commissioner Rick Nugent said.

“We have some very difficult weather conditions on Thursday and Friday,” he said.

“These conditions will make it far easier for fires to start and to spread and for existing fires to race off in the direction of the wind.”

Elsewhere in NSW, several small bush and grass fires have continued to burn across parts of the state but remain under control.

The fire risk set to ease in the lead-up to Christmas before a significant part of the state faces high fire dangers on Boxing Day.

South Australian firefighters urged residents to leave in the Onkaparinga Hills in the Mount Lofty Ranges as they battled an out-of-control bushfire on Monday afternoon.

They later downgraded their warning, telling residents to monitor conditions.

Regional areas across the state are expecting hot conditions on Boxing Day, with Adelaide facing a peak of 36C after a predicted 37C on Christmas Day.

Firefighters in Western Australia on Monday night upgraded a bushfire alert, warning residents it was “too late to leave” as a blaze intensified around 100 kilometres northeast of Perth, near the wheatbelt town of Northam.

Fires already burning across Victoria have the potential to worsen as extreme hot weather blankets most of the state on December 26, leading to authorities pleading with travellers to reconsider their trips.

“Our state will have all areas … in extreme fire danger rating, except for East Gippsland on Thursday,” Mr Nugent said.

Country Fire Authority chief executive Jason Heffernan urged those who can avoid travelling through those areas during the Christmas break to do so.

“If you do have to travel, have the VicEmergency app, you need to know where you’re going, and you also need to have that information available to you to be situationally aware,” he said.

About 100 fire personnel from NSW, the ACT, Queensland and Tasmania are set to arrive in Victoria to help battle the blazes.

Children rescued in floodwaters

Meanwhile in Queensland, three children clinging to a tree in floodwaters were rescued after more rain struck northern Australia.

However wet weather in Queensland has finally begun to ease in the countdown to Christmas.

Multiple crews were called after three girls sought refuge in the tree located in the flooded Barron River near Mareeba on Sunday night.

“There were three of them in the centre of the river hanging on to a tree about 15m out (from the river bank),” a Queensland Fire Department spokesperson told AAP.

The girls — aged 13 and 14 — are believed to have been part of a group of children who had been swimming in the floodwaters.

They clung to the tree for almost two hours before they were rescued about 7pm.

It marked the third water rescue in a wet couple of days in the rain-hit state.

Three girls swimming in floodwaters were rescued after clinging to a tree for almost two hours. Photo: QPS

Emergency crews were called to Granite Creek near Cairns on Saturday night, finding a 65-year-old man and his dog on the roof of a truck stuck in floodwaters.

The man was later taken to hospital to be assessed.

Earlier a 45-year-old man was rescued – then fined.

Crews retrieved the man after his vehicle was stuck in floodwaters near Bundaberg north of Brisbane on Thursday night.

“After checking he was ok, police determined the man had driven past multiple road signs before running into trouble,” a police statement said.

He was fined $838 and lost six demerit points for disobeying road access signs and driving without due care and attention.

“You cannot drive into floodwaters with the mindset of ‘it’ll be all right’,” Senior Sergeant Derek Garner said.

“Poor decisions can put your life, your family’s lives and emergency services’ lives at risk every time you decide to risk it.”

Roads were cut off during a wet week, capped by storms and intense rainfall across the tropical coast and Tablelands late on Sunday.

Mount Aunt near Mareeba was one of the worst affected, recording 156mm.

Flooding hit after some regions soaked up more than 340mm of rainfall in six hours.

The north Queensland region spanning Ingham to Proserpine recorded seven day rainfall totals ranging from 300mm to 500mm by Monday morning.

At one stage the deluge triggered flood warnings for 10 rivers across the state.

However, only a couple of warnings remained on Monday after the tropical low and coastal trough that brought widespread rainfall moved offshore.

Holiday-makers are set to return with flooded roads reopening including critical sections of the major arterial Bruce Highway.

A dry and sunny day is forecast across the majority of Queensland on Tuesday.

However, the Bureau of Meteorology said north of Cairns may receive isolated showers with the risk of a storm.

Isolated showers in Queensland’s central and north coast with possible storms inland have been forecast for Christmas Day.

-with AAP