Temperatures Soar Above 40 Degrees as Heatwave Grips South-East

Residents across the south-eastern states are being urged to beat the heat as temperatures exceed 40 degrees today.

Avalon Airport, in Victoria’s south-west, was the first site to hit 40 degrees at 10.21am, according to the Bureau of Meteorology, while Melbourne Airport reached 34.9 degrees just before 11am.

The scorching mid-morning temperatures come as an extreme heatwave grips much of the nation’s south-east, with some parts of Victoria set to experience their hottest day in three to four years.

Residents are bracing for tops of 45 degrees in Horsham and 43 degrees in Wangaratta while Melbourne, which reached 36.7 degrees at midday, is expected to soar to 42 degrees.

Gael Monfils of France cools down during a break in play against Novak Djokovic of Serbia during round two on day four of the Australian Open yesterday. (AAP)

United States' Denis Kudla uses a cool towel during a break while playing Austria's Dominic Thiem during their second round match yesterday. (AAP)If the city exceeds 42.2 degrees, this will be its hottest day since 2014, Weatherzone meteorologist Ben Domensino said.

Players at the Australian Open may have to spend time on the bench, after six-time winner Novak Djokovic described yesterday’s conditions as “brutal”, with temperatures on the court reaching 69 degrees.

“It was a big challenge for both of us to be on the court, to be able to finish the match,” Djokovic told reporters after stepping off the Rod Laver Arena furnace.

It is unclear whether the Australian Open extreme heat policy, which comes into effect if the ambient temperature exceeds 40 degrees and the wet bulb globe temperature exceeds 32.5 degrees, will be enforced today, with controversy over officials’ decision yesterday to not step in.

Little relief was felt overnight, with the mercury still at 32.2 degrees at midnight, and simmering around 30 degrees at 1am.

People braved the heat at Brighton Beach yesterday. (AAP)

Tennis goers did their best to keep cool on day four of the Australian Open in Melbourne yesterday. (AAP)T

Emergency services have been bracing for fires and ambulances being dispatched to treat people for heat-related illnesses.

“We’ll see heat impacts on people and infrastructure. It’s our summer but we need people to be tuned to where they are, to take care and to check in on others,” Victorian Emergency Services Commissioner Craig Lapsley said.

A total fire ban is in place across much of the state and 14 public parks are closed.

A severe heatwave is gripping much of the state's south-east. (9NEWS)

But the Bureau of Meteorology has touted a cool change for coastal parts of Victoria across the afternoon and evening.

Meanwhile, South Australia continues to cop the brunt of the extreme weather.

Temperatures are expected to soar towards 41 degrees in Adelaide and up to 45 degrees in the state’s north, prompting Tour Down Under organisers to move the start time up by an hour this morning.

The extreme heat has also forced organisers to cancel today’s Bupa Challenge Tour, which had attracted almost 5000 amateur riders from across the country.

Yesterday, the suburb of Roseworthy, north of Adelaide, recorded the highest temperature of the day at 43.3 degrees, with high temperatures continuing throughout the night.

Riders in the Tour Down Under struggled under the South Australian heat this morning. (AAP)

In New South Wales, parts of Western Sydney could be experiencing the start of their hottest four-day spell in more the 20 years today, according to Weatherzone meteorologist Ben Domensino.

Temperatures are expected to hit 29 degrees in the city and up to 41 degrees in the west.

As a slow-moving mass of hot air sweeps over NSW in the coming days, the mercury will continue to soar, elevating fire danger ratings.

Penrith is forecast to reach 41 to 43 degrees during the next four days, which would be its first four-day spell above 40 degrees in 23 years of records.

Richmond is also forecast to reach 40 degrees or more from today to Monday, although there’s a chance it will only hit the high-30s on the weekend.

Yesterday, Richmond had registered seven 40 degree days so far this summer, which is a new record up to this point in the season.

The previous record to this date was five 40-degree days in 1957 and 1958.

Fire crews are prepared for potential fires that may break out from the heat today. (AAP)

If Richmond does manage to reach 40 degrees on each of the next four days, the season’s tally will reach 11 days and match the current summer record from 2016 and 2017.

Eastern suburbs will also be noticeably warm in the coming days.

While sea breezes will keep the mercury much lower than the western suburbs, conditions will become increasingly humid, making it feel warmer than it actually is.

The extreme heat has fire crews on alert, mostly across northern Victoria and southern New South Wales.

Total fire bans are in place for all of central and western Victoria except for the Northern Country district, while the Department of Health and Human Services has issued health alerts for six districts today.

The Rural Fire Service has issued total fire bans in five areas across NSW today, including the Greater Sydney and Greater Hunter, while in South Australia, bans are in place for six districts across the state, including the Mount Lofty Ranges.

The searing heat is due to a tongue of hot air seeping across the nation’s southern states, as high pressure system moves out into the Tasman Sea.

A cool change is expected to sweep southern Victoria this afternoon, reaching Melbourne during the early evening before moving further inland tonight.

While the change will bring relief from the heat across southern Victoria, the shift in wind direction could pose a threat for any fires that are burning in the region.

What is a heatwave?

There is also a chance of the odd thunderstorm in northwest Victoria later this afternoon, which may exacerbate fight danger in parts of the Mallee and Wimmera districts.

Any relief in South Australia is expected to dip temperatures to around 35 degrees tomorrow.

Queensland are being spared the heatwave for now. But it is set to move across the state’s south-east early next week, with temperatures forecast to reach 34 degrees in Brisbane on Monday – the first day back for Queensland school students.

However, western Queensland has not been spared from the scorching temperatures gripping Australia’s south-east, with Thargomindah and Birdsville forecast to reach 46 degrees on Sunday.