Niwa forecaster Ben Noll told NZH Focus it could potentially be one of the hottest summers ever, but didn't wish to say so until the end of the season.
He did say they've seen widespread temperature differences from an average of more than 2C over the past few weeks.
Those places include Auckland, Whangarei, New Plymouth and Invercargill.
When asked how the rest of summer is looking, Noll is less optimistic.
He says the weather looks likely to become wetter, and sunny weekends are likely to be few and far between.
Noll points to the coming weekend - Auckland Anniversary - as one in particular that beachgoers ought to make the most of. Parts of the South Island also look set to bask in sunshine too, he says.
"As we go into February, things are likely to turn a bit more average."