NIWA says Auckland Anniversary weekend is set to be the exception, with thunderstorms and rain either side.
Days at the beach are numbered, as Kiwis are facing a muggy, wet remainder of the summer.
The month of December was the second hottest on record, and January so far, according to Niwa, looks set to break records.
One climate scientist, Jim Salinger, believes if the average temperature forthe month slides up only half a degree, it may be the hottest month since records first began.
The weather looks likely to become wetter, and sunny weekends are likely to be few and far between, says Ben Noll. Photo / Michael Craig
The average January temperature is 17.1 degrees centigrade, the average so far for January 2018 was 19.3C - the hottest since records began in 1909.
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."
