Weather Warning: Australia Braces For Scorching Temperatures And Severe Fire Danger

Parts of the country will sweat through temperatures of up to 40 degrees on Friday, with a heatwave sparking severe fire danger across Australia.

Temperatures in NSW are forecast to hit the mid-40s, peaking on Friday and Saturday, The Bureau of Meteorology said.

NSW has three fire bans in place on Friday as hot, dry and windy conditions are forecast for the weekend.

With very high fire danger expected, the Orroral Valley blaze in the ACT could cross the border into NSW, the Rural Fire Service said.

NSW Police have issued an alert for "extreme" heat across the state for the next three days.

State Emergency Operation Controller, NSW Police Force Deputy Commissioner Gary Worboys, urged those cooling off by the water to stay safe.

Sydney siders enjoying the beach. Image: Getty

"Anyone swimming in unfamiliar waterways is urged to take extra care – every year thousands of people require rescuing from the surf and many needlessly drown,” Deputy Commissioner Worboys said.

“I want to send a strong message to parents: if your children are out swimming, whether that is at the beach, a river, a dam or your backyard pool, and regardless of their age – they need to be supervised," Worboys said.

It will be so hot in Melbourne on Friday that it'll feel more like Darwin, forecasters warned, with temperatures climbing in the 40s.

Damaging winds and dry lightning are expected to raise the fire threat in Victoria after a week of calmer conditions.

The merry-go-round weather experienced a week ago is set to return, with Melbourne's forecast 43C expected to give way to possible flash flooding and muddy rain over the weekend.

CFS members put out a fire which reached Hay bails on a property at Mount Torrens in the Adelaide Hills on January 3. Image: AAP

The heat burst will also hit South Australia with the added rainfall causing humid conditions.

Very high bush fire conditions have been declared for 12 South Australian districts.

Brisbane will face temperatures in the 30s, while further north in the state, monsoonal rains continue through the weekend.

Cooler weather is forecast for Perth, with a sunny weekend bringing temperatures in the 30s.

Hobart will see the mercury scorching to 40 degrees with blazes at St Marys and North of Rossarden at Advice level.

With AAP