Live updates: Extreme weather grips Australia; Heatwave sweeps southern states; Fires trigger emergency warnings; More rain for flooded Queensland

We will leave the live updates here, thank you for following along.

There are two major bushfires burning in Victoria, in Longwood and in Walwa, in the state's north-east.

The fires are both still burning and remain out-of-control.

The latest advice for towns in and around both areas is to leave immediately.

Tomorrow is expected to be a catastrophic bushfire day as temperatures climb to above 40 degrees and our live blog will return early in the morning.

You can find the most up-to-date advice and warnings here.

For more reporting on the fire emergency, click here.

Strong winds are fanning flames from the Longwood fire in a south-easterly direction, sparking evacuation warnings for more than a dozen towns.

Residents in Avenel, Dropmore, Highlands, Ruffy, Tarcombe, and Upton Hill have been urged to take immediate shelter.

Those in Cathkin, Caveat, Dropmore, Fawcett, Ghin Ghin, Gobur, Highlands, Kanumbra, Kerrisdale, Killingworth, Koriella, Merton, Molesworth, Tarcombe, Terip Terip, Trawool, Whanregarwen, Whiteheads Creek, Woodfield and Yarck should leave their homes immediately towards Seymour or Yea.

A watch and act warning has been issued for Alexandra, Bonnie Doon, Devils River, Eildon, Fawcett, Howes Creek, Karralika Heights, Koriella, Lake Eildon, Maindample, Maintongoon, Mansfield, Snobs Creek, Taylor Bay, Thornton, Whanregarwen, Woodfield.

Residents there should prepare their belongings to leave the area.

The bushfire is expected to continue to extend in a south-easterly direction towards Lake Eildon, the CFA said.

Residents impacted by the Longwood bushfire have filtered into an emergency relief centre in Seymour.

Drew and Debra Birrell and their two children drove to the Seymour Sports and Aquatics Centre this morning after escaping a "big distinctive smoke haze" surrounding their Locksley home.

"It was a pretty easy decision, it's just something you've got to live with out in the bush. You just prepare your house the best way you can," Mr Birrell said.

"You've just got to let nature take its course. If it's going to burn, it's going to burn."

The family doesn't know how long they'll remain in Seymour.

"We just packed up what we knew we needed and couldn't replace and then just came here," Mr Birrell said.

"You can't put a timeline on Mother Nature."

The Longwood fire has now spread across 3000 kilometres and is burning across bushland in southerly and westerly directions.

The catastrophic fire danger declaration in Victoria has triggered a "red escalation", the highest level of emergency response activation for Ambulance Victoria.

First responders and paramedics will be relocated from branches that are within the fire danger zone, including those with proximity to bushland and limited road access.

"Crews will only be redeployed into these zones in the case of serious or life-threatening illness and only after a thorough risk assessment to consider the safety of our people," Ambulance Victoria said in a statement.

Residents have been told to leave now or by 7am tomorrow at the very latest in the fire danger zones around Walwa and Longwood.

Authorities are concerned tomorrow will be catastrophic ahead of temperatures reaching well above 40 degrees, mixed with dry and windy conditions.

While today saw two major bushfires burn uncontrollably in Victoria's north-east, the worst is yet to come.

"Tomorrow is a very, very dire bushfire day in the state of Victoria," CFA fire chief Jason Heffernan said.

"Do not wait for a warning. You must be ready to take action and enact your bushfire survival plan."

Residents in towns in and around Longwood have risked their lives to help their neighbours and protect livestock as an out-of-control bushfire rages on.

Several roadblocks have been set up here to prevent people from going into the fire zone, however some have ignored it to return to their homes and communities, 9News reports.

Some livestock have already been sadly lost in the blaze.

Evacuees who have left their homes have moved to a relief centre in Seymour.

The Country Fire Authority (CFA) advice is to leave immediately.

A very different weather system is brewing in Queensland.

The Bureau of Meteorology has warned there is a 40 to 50 per cent chance a tropical low hovering near the state's coast could become a tropical cyclone before it reaches land.

Whether or not it develops into a cyclone, the tropical low is forecast to bring significant rain across Queensland's coastline.

A severe weather warning has been issued for parts of the east coast, including for heavy rainfall, flooding and damaging winds.

"It stretches from north of Cooktown, past Port Douglas and Cairns, through Townsville, Ayr and Bowen and comes all the way down to Hamilton Island," meteorologist Angus Hines said.

"In this area we could see heavy to intense rainfall, including the possibility of 100mm rainfall totals in a six-hour period during the day on Friday, and up to 250mm over a 24-hour period.

"Persistent heavy falls between Christmas and today have meant that rivers in the north are flooding already, Hines added.

Renmark in South Australia's Riverland region has smashed a 30-year record after hitting 47.2 degrees today, its hottest January day since 1996.

Tomorrow will bring another sweltering 47-degree day for the Murray River town.

Meanwhile, Swan Hill in Victoria's north-west reached 45.8 degrees, its hottest January day in seven years.

The advice is to leave immediately for residents in areas impacted by the Longwood fire, which is out of control and is continuing to spread.

This emergency warning has been issued for Avenel, Creightons Creek, Euroa, Gooram, Locksley, Longwood, Longwood East, Old Longwood, Ruffy, Tarcombe and Upton Hill.

The bushfire is travelling from Longwood in an easterly direction towards Crightons Creek.

"Emergency services may not be able to help you if you decide to stay," the CFA said in an update.

The Hume Freeway is closed between Violet Town and Avenel.

Avenel-Longwood Road and Clarkes Road remain open.

Sydneysiders are among those in NSW being told to take appropriate steps to prepare for a heatwave that will last into the weekend.

Temperatures are set to hit 33 degrees in Sydney today, and will soar in the coming days as a hot airmass moves across the state.

The mercury is expected to reach 42 degrees on Saturday in the state capital, with similar temperatures expected in many areas of NSW.

Whilst the heat is expected to ease off on Sunday, NSW Ambulance's Steve Vaughan warned having such a long stretch of heat will take its toll.

Read more here.