Sydney, Melbourne, Brisbane weather: Brutal heatwave about to strike as aircon warning is issued

A second heatwave in as many weeks is about to strike Australia with much of the country set to bake in sweltering temperatures from Friday through to the weekend. 

The Bureau of Meteorology has issued heatwave warnings covering large swathes of NSW, Queensland, the NT and WA.

Weatherzone meteorologist James Rout told Daily Mail Australia that 'Saturday looks like it will have the hottest temperatures which will continue into Sunday'.

'On the east coast the main affected areas will be southeast Queensland and northeast NSW,' Mr Rout said.

'Sydney will be hot today, especially in the west of the city which will hit the high 30s this afternoon, but a southerly change should come through about 9pm tonight that will see temperatures cool'.

Concerns about energy reserves today has prompted the  NSW government to urge the community to reduce usage between 5 and 9pm.

NSW residents have been asked to consider turning off their airconditioning during that time, and delay using non-essential appliances such as dishwashers and washing machines on Thursday night.

Temperatures in western Sydney arae set to hit 40C on Friday, and the mercury will rise to 37C in Sydney city. 

According to Weatherzone temperatures on the weekend will hit the mid to high 30s over much of southeast Queensland and northeast NSW with a few places like Ipswich, west of Brisbane, likely to hit 40C.

'The overnight temperatures should stay quite warm as well, especially towards the coast, so Brisbane will have hot and sticky nights.'

Tropical Cyclone Jasper has hit the north of the state so areas around Cairns have been battered by gale force winds and heavy rain since Wednesday.

More than 17,000 homes and businesses were without electricity on Wednesday night and flash flooding remains a concern. 

The category 2 cyclone should have passed by Thursday afternoon with cleanup efforts set for the weekend.

Mr Rout said over in WA and the NT the heatwave will be in full swing with 'lots of places to hit the mid-40s on Friday and the heat will spread over the weekend.'

'Half of the state will be between 40C - 45C on Saturday and Sunday, though it will be mainly inland and not to focused on Perth.'

The WA capital should see temps in the high 30s over the weekend with the inner west even hitting 40C.'

'There should be sea breezes over the city in the afternoons to cool things off a bit.'

Mr Rout said Melbourne and Adelaide should avoid the hot weather and the heatwave temperatures should ease from Monday so next week will be more comfortable for the rest of the country.