Break out the jandals and togs! There's a heatwave coming for NZ this weekend!

A heatwave is heading straight for New Zealand after bringing scorching temperatures to Australia.

The heatwave on Saturday in Sydney will drift over the Tasman Sea to the South Island on Sunday, then the North Island on Monday.

Temperatures are predicted to soar as high as 40C through inland New South Wales, and Sydney may hit 36C. Their Government forecaster, the Bureau of Meteorology, reported it would be the first time in history the state has reached 40C in the month of September.

The heatwave should lose around 10C by the time it reaches New Zealand, making for balmy temperatures in the late 20Cs and early 30Cs, WeatherWatch head analyst Philip Duncan said.

"The air loses a lot of warmth as it leaves hot inland Australia and crosses over the cooler waters of the Tasman Sea. It then warms back up again a bit as it crosses over the ranges of New Zealand."

"If New South Wales is heading to 36 to 40 degrees this weekend it's fair to suggest that the east of the North Island will climb into the mid to late 20Cs.

"I don't expect 30 degrees here, but, I also can't rule it out as the ingredients are there under perfect conditions to climb that high."

WeatherWatch suggested inland Hawke's Bay may reach the mid 20Cs on Monday, but the nor'wester will heat up some areas even higher.

This article was first published on nzherald.co.nz and is republished here with permission.