“A blistering day for the state capital,” the Bureau of Meteorology senior meteorologist Angus Hines said.
“And all of the suburbs around the Sydney metro area forecast to reach the high 30s.”
He warned some areas might “flirt with 40C” today.
“We’ll be looking at record temperatures around the Sydney area for this time of year,” he said.
Other areas along the NSW coast will also feel the heat, with Gosford and Newcastle forecast to hit 39C and Wollongong expected to sizzle at 37C.
“It will be a hot day right across the New South Wales Tablelands and Western Slopes as well,” Hines said.
“Many locations through these parts could be 12C to 15C higher than their October average temperature.”
It will also be extremely windy across NSW today, on Wednesday, with damaging gusts expected to hit the llawarra, South Coast, Snowy Mountains and parts of Metropolitan, Central Tablelands, Southern Tablelands, South West Slopes and Australian Capital Territory Forecast Districts.
Wind is expected to reach speeds of 90km/h across the central ranges and metropolitan regions, though may be in excess of 100km/h in some areas.
“Conditions begin to ease about southern warning areas late Wednesday evening, easing about central areas early Thursday morning,” the bureau said.
The bureau has issued a fire weather warning for the Greater Hunter, Greater Sydney Region, Illawarra/Shoalhaven and Upper Central West Plains fire districts.
“West to northwesterly winds will shift west to southwesterly across the west and south during the day,” the warning read.
“Thunderstorms are possible with strong and potentially damaging wind gusts.”
Forecasters warned that the hot temperatures combined with the strong and destructive winds could produce extremely dangerous conditions.
Fire bans in Queensland, NSW
The extreme conditions have sparked fire warnings or bans in several states.
The NSW Rural Fire Service declared a ban in Greater Sydney, the Illawarra and Shoalhaven, Greater Hunter, Upper Central West Plains and North Western areas on Wednesday.
Firefighters warned that the extreme hot, dry and windy conditions expected across parts of the state would increase the risk of fires.
A fire ban has also been enacted by the Queensland Fire Department for much of the state’s northeast. Impacted areas include Townsville, Burdekin Shire, Mackay, Isaac, Central Highlands, North Burnett, Banana Shire, Gladstone, and Bundaberg regions.
A total fire ban is in place for residents in Far North Queensland, spanning the Northern Peninsula and Kowanyama Aboriginal Shire.
Victoria smashed by blistering winds
Blistering and damaging winds are forecast to smash much of the southeast regions today, with Victoria forecast to bear the brunt of the gusts.
Almost the entire state has been hit with a severe wind warning, with gusts reaching in excess of 120km/h developing over the southwest on Wednesday afternoon.
The city will see winds averaging speeds of 60km/h, though peak gusts could be in excess of 100km/h in the afternoon and evening.
The most destructive winds reaching speeds of 130km/h are forecast to hit Cape Otway late this morning.
The bureau forecasts Geelong, the Mornington Peninsula and south Gippsland will be hit with damaging gusts up to 120km/h this afternoon, while 100km/h gusts sweep through Melbourne.
Residents are advised to stay indoors during the extreme wind, and remain clear of loose items and windows.
“Winds of this speed can take down trees or certainly large branches, can cause power outages, can make for dangerous driving conditions, and can of course damage cars and property,” Hines said.
On Tuesday night, millions of people were warned to power their mobile devices before destructive winds blast through Victoria.
Emergency Management Commissioner Tim Wiebusch said Victoria had not seen winds like this for quite some time.
“We’re asking Victorians to be prepared for power outages, that means be aware of power lines that may be on the ground,” he said.
“Make sure you have charged your mobile devices tonight so that you can survive through those power outages.”
Week of record-breaking heat
The ongoing heatwave comes after record-breaking temperatures on Monday, with scorching temperatures reported across Queensland, South Australia and NSW, exceeding the monthly average by as much as 15C.
Sign up to Herald Premium Editor’s Picks, delivered straight to your inbox every Friday. Editor-in-Chief Murray Kirkness picks the week’s best features, interviews and investigations. Sign up for Herald Premium here.