Prime Minister Tony Abbott has done his level best to keep climate change off the G20 agenda for this weekend's leaders summit but it seems nature is going to have the final say.

The heatwave that's been building for days across outback Australia will make a timely arrival across south-eastern Queensland from Friday until at least Monday.

The same searing heat will bring temperatures of 45 degrees or more in parts of NSW on Friday and send the mercury towards 40 degrees in parts of western Sydney. Sydney itself is forecast to cop a 35-degree maximum.

Victoria gets its share of the warmth on Thursday with 34 degrees expected for Melbourne and 40 degrees in Mildura in the state's north-west.

'Extreme heatwave'

According to the Bureau of Meteorology's pilot heatwave project – which measures heat extremes compared with preceding periods and historical data – areas around Brisbane will experience an "extreme heatwave" during the main meeting days of Saturday and Sunday.

The mercury is forecast to reach 32 degrees on Friday in Brisbane before climbing to 35 on Saturday and 36 degrees on Sunday and Monday. The city's average maximum in November is 27.8 degrees.

"The last time we had three days of 35 degrees in a row in Brisbane in November was in 1968," said Ben McBurney, a meteorologist with Weatherzone. "It's certainly earlier than we'd expect."

Only the timing of a sea breeze on each day, particularly Saturday, is likely to prevent temperatures soaring, he said.

Mr Abbott has sought to steer discussions at the G20 summit towards efforts to generate faster global growth, relegating climate issues to sessions dealing with energy efficiency.

Setbacks

The government's bid to avoid climate change had already suffered a setback with Wednesday's announcement that the US and China would both step up efforts curb carbon dioxide emissions in a bid to avoid climate change.

Journalists are likely to press the Australian government for comments on its climate policies not least because of this week's breakdown in talks with Labor to cut the country's renewable energy target.

Meteorologists and climate experts are, of course, wary of reading too much into any weather event. Still, it may be a nuance lost on delegates who stray far from their air-conditioned conference cocoons, hotel suites and limousines.

Weatherzone is owned by Fairfax Media, publisher of this website.