Smoke is wafting over parts of Sydney this morning as several large bushfires burn across Victoria. 

The NSW Rural Fire Service says coastal areas are most likely to be impacted with conditions to clear by midday. 

An aerial shot from our chopper has captured the haze of smoke blanketing metropolitan Sydney this morning. 

"We should see that smell of smoke start to ease as the winds pick up over the course of the day and that smoke will clear," Emily Cook from the NSW RFS says. 

Canadian firefighters are likely to be deployed in Victoria's north as heatwave conditions continue.

Forest Fire Management Victoria state agency commander Dave Sayce told ABC Melbourne 774 the Canadian crews had arrived Tuesday and today.

"Some of these men and women from British Columbia and Alberta are of course coming from their winter to near-on 35 degrees … some of these crews are likely to be deployed up to the north of the state, which is still in extreme heatwave conditions," he said.

He said overall about 1,300 overseas and interstate firefighters had joined Victoria's firefighting efforts in recent weeks, including personnel from New Zealand.

Mr Sayce said working in extreme heat was hard on firefighters.

"If you can imagine being in full PPE against radiant heat with those temperatures, it was certainly very tough," he said.

A number of heatwave warnings remain in place today, with NSW Ambulance urging residents to limit their time outside.

Temperatures are set to hit the low-mid 40s in the Central West Slopes.

In the hub of western NSW, Dubbo is set to hit 44C after the mercury hit a record 46.1C on Tuesday. 

Further inland, Broken Hill is expected top 45C by midday after enduring its hottest day on record yesterday as temperatures reached 47.8C.

Residents in the Snowy Mountains and the Upper Western are also urged to stay hydrated and monitor for signs of heat-related illnesses. 

Chris Smith, who owns a property in Gellibrand near the Carlisle River fire, told ABC Melbourne 774 how visibility was severely impacted as a wind change swept through Victoria's Otways late Tuesday afternoon.

He said he was well set up to respond to spot fires on his property.

"We were fully prepared, we had hoses out, all our generators running, all that sort of thing, but for us what was so concerning was the wind changed and everything went smoky so you couldn't see," he said.

"You simply couldn't see. You could see 50 to 100 metres, but you couldn't see across the farm to know where to go to.

"It's that concern of not knowing what might be burning, where."

He said the greatest damage to his property had been a "pristine" piece of bush razed by necessary efforts to control the fire with a bulldozer.

"This area of bush, they had to come in and then put a ring around the fire," he said.

He said the loss of other people's homes in the area was "immense" compared to the scale of damage on his property.

"For everyone impacted by fires ... I just wish them all the very best," Mr Smith said.

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The Carlisle River fire in the Otways in Victoria's south-west has grown to more than 11,000 hectares after it broke containment lines and spread across the Colac — Lavers Hill road yesterday.

Overnight incident controller Peter Shaw says cooler conditions this morning will allow crews to assess the fireground with the aim of returning people back to their homes.

"Today the winds are far lighter… and also coming round more from the south so pushing the fire back onto itself,"

"We're going out with crews this morning in the daylight to do some better assessments and the view is we will consolidate some lines … looking at starting to open up some of the area to let the public back in.

"Gellibrand has had some fire across the roads … at this stage we are assessing if any buildings have been damaged. We are expecting that there will be some."

Colac Otway Shire Council Mayor Jason Schram said there were about 160 residents in their evacuation centre, many of whom were "anxious" to hear about the fate of their properties.

"Prior to yesterday, we'd lost three homes and I have heard of structure losses overnight when that horrific wind change came through," he said.

"It's just a matter of getting the crews in there and assessing that and hoping it's minimal."

A Total Fire Ban has been declared for the Central Ranges today due to forecast hot, dry and windy conditions.

The ban covers Bathurst, Blayney, Cabonne, Cowra, Lithgow, Mid-Western, Oberon and Orange. 

No fires may be lit in the open and all fire permits are suspended.

The town of Gellibrand, near the Otways fire in Victoria, will run out of tap water today.

Barwon Water warned residents last night that the Gellibrand water treatment plant had been impacted by fire.

"This means by the early hours of Wednesday 28 January there will be no tap water available in Gellibrand, and the remaining water remains unsafe to drink," the authority said.

They said an update would be given about 11am AEDT today.

Gellibrand is currently under an Emergency Warning due to the fire. Residents still in the area have been urged to take shelter now as it is too late to leave.

Tens of thousands of people across Victoria remain without power, with the majority of outages in the state's east.

Ausnet, which provides power to the east of the state, lists 20,400 customers affected by unplanned power outages, while Powercor, which services the west of the state, including parts of Melbourne, says close to 3,000 customers are affected by unplanned outages.

Jemena, which services parts of Melbourne, has more than 2,600 affected customers and United Energy, which covers parts of the city's east and Mornington Peninsula, lists just over 3,000 customers experiencing unplanned outages.

While Queensland's north shelters from floods and heavy rain, the state's west and south are sweltering through a potentially record-breaking heatwave.

Yesterday was the hottest day in 12 years for parts of South West Queensland, with St George reaching 45.7 degrees Celsius and Thargomindah hitting 46.6C.

The BOM says a stagnant air mass locked in place for several days has caused the extreme conditions, which are likely to peak in South West Queensland today.

Thargomindah in the state's south-west could set its all-time heat record, with temperatures up to 49C predicted.