Adelaide's 80-year-old heat record could topple this week with South Australia braced for soaring temperatures and extreme conditions.

The city's highest recorded temperature currently stands at 46.1C, but John Nairn of the Bureau of Meteorology said that figure could be challenged by a forecast high of 45C on Thursday.

"When we go to a number like that we have to be cognisant that there's two records that we've got for Adelaide," he said.

"One on East Terrace (Kent Town) in 2009 where we got to 45.7 and the other on West Terrace in 1939 where we reached 46.1.

"Those numbers are not far from being reached on Thursday."

One nine.com.au reader, who is without an air conditioner, found a novel way to keep herself cool.

Thursday will mark the last of three days of SES-issued extreme heat warnings, with the temperature expected to reach 40C on Wednesday.

(Nine.com.au Facebook)

While South Australians are expected to bear the brunt of this week’s heatwave, conditions are equally sticky around the rest of the country:

NEW SOUTH WALES

Much of the state is set to swelter through temperatures in the mid to high 30s, with some regional areas expected to hit 40 degrees as South Australia’s heatwave moves eastward.

There are possible afternoon storms for coastal areas that may bring relief for residents.

Sydney’s city is expected to hit a top of 29 degrees, while the hottest part of the state is expected to be Wilcannia in NSW’s upper western region, where the temperature is set to hit an astonishing 45 degrees.

VICTORIA

Residents in Melbourne are expected to enjoy more temperate conditions today, with a maximum temperature of 25 degrees and clearing clouds in the city’s CBD.

Regionally, the Mallee region of the state is expected to see the highest temperatures with tops of 41 degrees in Mildura.

QUEENSLAND

Queenslanders are set to endure another humid summer day, with hot temperatures and cloudy conditions forecast for much of today.

In Brisbane residents can expect an overcast day with highs of 34 degrees, while those in the northern cities of Cairns and Cooktown can expect multiple tropical showers and temperatures in the low 30s.

The hottest part of the state is expected to be Birdsville in QLD’s Channel Country, where temperatures are set to hit an overwhelming 46 degrees.

WESTERN AUSTRALIA

Much of Western Australia’s northern coastline is expected to experience multiple summer storms, with showers and lightning predicted for Broome, Derby, Marble Bar and Exmouth.

Beachgoers are being warned to avoid the hottest part of the day and keep hydrated. (AAP)

Down south, in the capital of Perth, residents can expect a windy day with multiple showers and tops of just 22 degrees.

NORTHERN TERRITORY

Territorians are just battering down for the beginning of monsoon season, with a weak trough extending across the Top End and the Cape York Peninsula.

A man keeps cool in the water at Glenelg beach during yesterday's scorcher in Adelaide. (AAP)

Those in Darwin can expect rain all days, with tops of 31 degrees. The hottest part of the territory is expected to be Alpurrurulam in the Barkly region, where temperatures will hit a maximum of 44 degrees.

ACT

All of the ACT is expecting a humid and stormy day today, with temperatures exceeding 30 degrees in almost every region of the territory.

Canberra’s city centre is expected to hit 34 degrees with a shower or two developing in the afternoon.

TASMANIA

Emergency warnings have been issued for six areas in central Tasmania, with lives and properties at risk, as weather conditions continue to worsen.

Temperatures at 1pm around the country are expected to be dangerously high. (Windy.com)

The Tasmania Fire Service early on Wednesday morning warned residents of Miena, Barren Tier, Tods Corner, Penstock Lagoon, Liawenee and Shannon that they may be in danger and need to take action immediately.

A property has already been lost near Miena, the TFS confirmed on Tuesday night.

Almost 50 fires are burning across the state and though conditions had eased, more winds and high temperatures were expected by the end of the week.

Residents in the line of fire are being told to be on alert for embers, smoke and ash and dozens of people have already moved to evacuation centres.