It's official - this summer is already the hottest on record, with four days still to go, according to new data from the climate agency Niwa.
Summer temperatures have been 2.3°C hotter than average, 0.5° above the previous record, which dated back more than 80 years.
Niwa meteorologist Ben Noll said with summer not yet ended, it was likely the record-breaking average would push higher.
The big driver has been the marine heatwave - a signature of La Niña weather pattern.
"Our oceans around New Zealand have featured excessively warm conditions in the order of of two to four degrees above average and in some pockets six or seven degrees above average.
"As an island nation, as the seas go, we go."
These freakishly warmer seas, together with northerly winds from the tropics and sub-tropics, have ratcheted up the temperature and that was expected to continue through autumn, he said.
However, climate change was definitely a factor.
"If you had the same conditions, the same atmospheric set-up two or three decades ago, it's unlikely you would have experienced the anomalies or the difference from average being quite as extreme as it was in 2017/2018.
"And that's indicative of the long-term trend of global climate change, global warning."
New Zealand could expect to see increasing numbers of heatwaves and droughts in the coming decades, he said.
The country may continue to bask in warmer temperatures through autumn because because oceans cool more slowly than land.
"But this can also mean more fuel for weather systems [storms] tracking towards New Zealand from the tropics and sub-tropics....
"Sometimes it's too dry, sometimes it's too wet. This summer we've experienced both of those extremes."
Summer standouts so far:
- Across New Zealand 108 places recorded their hottest summer on record, 21 their second hottest and eight their third hottest.
- In Alexandra on 30 January the temperature reached 38.7°. On the same day Clyde got to 37.6°, Middlemarch 37.4° and Cheviot 37.3° - together these comprise the hottest temperatures of summer.
- Wellington has had 17 days above 25° this summer - the average is two.
- Auckland usually has 29 summer days above 25°, this year there have been 47 - the highest since records began at Auckland Airport in 1966.
- Invercargill recorded three consecutive days over 30° in January. It's never done that for two days in a row, let alone three.
- Cromwell has topped 25° for 56 days - normal is 35 days.
- Dew point temperature - the meteorological measurement combining humidity and temperature - failed to drop below 19° in Auckland from 10 - 15 February, making it a rare 115-hour period of very high humidity.
- In Wellington, there was a dew point temperature of 22° at 6pm on 11 February, the highest dew point on record for the city.
- Mahia, Appleby and Waipara West have had their wettest summers on record.