SWAN HILL will endure its third consecutive day above 40 degrees today, with the mercury expected to reach a scorching 47 degrees.
If the maximum high is reached, it will be Victoria's hottest December day on record, surpassing the current record set in Robinvale in 1976 at 46.6 degrees.
There will be a minimum of 21 degrees, with winds north to northeasterly 20 to 30km/h in the morning before turning northwesterly 15 to 25km/h in the middle of the day.
The extreme heat has forced four states to be issued weather warnings, with strong winds, severe thunderstorms and dangerous fire conditions predicted over the next 24 hours.
NSW Premier Gladys Berejiklian issued a State of Emergency yesterday morning, lasting seven days under section 33 of the State Emergency and Rescue Management Act.
The declaration will enable the Rural Fire Service (RFS) Commissioner Shane Fitzsimmons to exercise extraordinary powers to protect life and property.
"Declaring this State of Emergency is vital to the safety of communities in NSW as we face the most devastating bushfire season in living memory having lost six lives and almost 800 homes destroyed," Ms Berejiklian said.
"These declarations are not taken lightly. This is the second State of Emergency this season following the declaration made on November 11, also for a period of seven days."
Meanwhile, the entire state of Victoria has also been issued a total fire ban for today meaning no fire can be lit in the open air or be allowed to remain alight in the open air including campfires and burn offs.
All general purpose grinding, welding, soldering or gas cutting works in the open air are also prohibited.
Total fire bans were declared for the entire state of NSW from December 18 until tomorrow.
State response controller Gavin Freeman urged all Victorians to be aware that fires can happen anywhere without warning and to make plans accordingly.
"Hot and dry conditions are expected across the north today, with escalating fire risk across the state," he said.
"We already have several fires burning in East Gippsland and we certainly want to avoid any new fires starting."
Mr Freeman said all Victorians should take action to protect themselves from the heat and look after those most at risk.
"This includes your neighbours living alone, the elderly, the young, people with medical conditions and don't forget your pets," he said.
"Extreme heat kills more Australians than any natural disaster and can affect anybody. Be sure to stay hydrated, keep cool by seeking our air conditioned area and always check on others."
The Bureau of Meteorology is forecasting a cool change late today in the southern parts of the state, but hot and dry conditions will remain across Victoria's north until Sunday.
