Multiple states are sweltering through a low-intensity to severe heatwave with some temperatures expected to exceed the high forties.
Parts of Queensland, Tasmania, South Australia, and Western Australia are all preparing to be scorched by severe summer conditions over the weekend.
WA and Queensland have been sizzling for some time, but the conditions are now extending into the southeast, the Bureau of Meteorology's Miriam Bradbury told AAP.
It won't be as hot this weekend as last, but inland parts of NSW, Victoria, Tasmania, central Australia and WA may experience severe heatwave conditions.
A heatwave is when temperatures are above average during the day and night over a period of three days or more.
For Tasmania, temperatures will reach the low 30s during the day and high teens during the night.
"That doesn't sound warm for mainland Australians but compared to the averages of Tasmania that is still significantly more," Ms Bradbury said.
In parts of central Australia, inland Queensland and WA temperatures will be eight degrees above average to between 40C and 44C.
The conditions have elevated the bushfire risk with fire danger ratings across most of the nation remaining at moderate to high.
High is before the extreme rating which is when total fire bans are issued.
"With moderate to high we're still below warning level but it's not a sign to let our guard down as we all know how bushfire-prone Australia can be in the summer period," Ms Bradbury said.
Tasmania, southwest WA pushing into SA and western Victoria will experience the most risk of fire danger over the weekend.
"Particularly through western Victoria, where we've seen so recently those really terrible bushfires in the Grampians, is one to have on people's radar," Ms Bradbury said.
While a large swathe of Australia will swelter, east coast cities such as Sydney and Brisbane will have a wet weekend.
Temperatures will reach into the high 20s, but humidity will be rampant as an easterly flow pushes from the east coast.
The showers and storms already impacting the east coast for a number of days will continue with heavy falls around Sydney on Friday, while the wet weather will increase in Brisbane on Saturday.
The bureau is forecasting showers and thunderstorms with some severe conditions that bring the risk of flash flooding and for Brisbane, damaging wind gusts and hail.
"For all our east coasters, it's certainly a weekend to be keeping an eye on the radar," Ms Bradbury said.
A flood watch is already in place for Sydney's Hawkesbury Nepean River as the wet weather continues over the weekend.
Ms Bradbury warned rain expected on Friday may cause minor flooding in parts of the river system.
