"If the air temperature is 46°C, imagine what the heat is like in the sun on the footpath - the heat will be incredible. This is something."
Mr Duncan said that the same high pressure system that fed hot winds into Sydney was bringing the cold south-westerlies that had brought a cold change to much of New Zealand.
The system would change as it moved across from Australia, and would bring hotter temperatures from Canterbury to about Marlborough today. "We get the watered-down version that has to travel all the way across the Tasman Sea ... it doesn't have the same oomph."
However, this weekend the beginning of a transition to more normal summer temperatures would occur.
By Monday a high pressure system would have built over New Zealand, bringing fine and settled weather for most of the country.
"Once next week arrives, we are pretty much getting locked into a summer weather pattern for the rest of January," Mr Duncan said.
"The heat will come back quite quickly in some areas. It looks like we're going to have a series of highs that are going to linger around the country right through Auckland Anniversary Weekend."
Mr Duncan said while such an outlook was good news for those on holiday, some regions faced the prospect of a potential late-season drought.
Read more: The Big Day Out NZ missed