While temperatures in most of the main centres hovered around the late teens or low twenties today, Dunedin's high was 26C.
WeatherWatch head analyst Phil Duncan said, overall, temperatures were higher than average, because of a big high to the north of New Zealand spinning anticlockwise and bringing weather from Queensland and as a far away as New Caledonia.
"September and October were warmer generally. It's normal spring weather but warmer than usual."
Duncan told the Herald the North Island had been wetter than usual, whereas Canterbury's drought was continuing.
The high temperatures indicated Kiwis could be in for record-breaking highs this summer, Duncan said.
However, the immediate forecast was less promising. The week ahead would be "a bit unsettled".
"It's quite complicated. It's a messy set up on Thursday and Friday."
Tauranga would buck the trend, with warmer weather set to stick around.
"They've got a great week on the way. The rain's not really much of an issue for the Bay of Plenty."
Temperatures in Christchurch would creep up to 24C on Wednesday, but then dip to 11C on Friday, Duncan said.
"Dunedin's in typical spring mode. Today was their hot day."
Temperatures in the city would fall to 19C tomorrow, before dropping another few degrees to 11C later in the week.