It will not come as any surprise for Central Otago and Strath Taieri residents.
New Zealand's top three hottest temperatures for the summer were recorded on January 30 in Alexandra (38.7degC), Clyde (37.6degC) and Middlemarch (37.4degC).
And Invercargill recorded temperatures over 30degC for three consecutive days in January. It has never done that for two days in a row, let alone three.
Niwa meteorologist Ben Noll said until now, the hottest New Zealand summer on record was in 1934/35 when the temperature was 1.8degC above average.
This summer was running at 2.3degC above average - 0.5degC above the previous record.
Mr Noll said the driver of this summer's ''remarkable'' warmth was the marine heatwave.
''This has been a striking feature on both a regional and global climate scale.
''It began at the end of November last year and has now persisted for three months.
''There have been three distinct peaks when sea surface temperatures were between 2degC and 4degC above average - mid-December, late January and mid-to-late February.''
He said there were some areas around the Otago coastline where sea surface temperatures were as high as 7degC above average.
''This represented some of the largest ocean temperature anomalies anywhere in the world over the last several months.''
Mr Noll said a warmer than average Tasman Sea was a signature of La Nina, and was associated with higher than normal air pressure over the region during the late-spring and early-summer.
It prevented mixing of deeper, cooler sea water with warmer surface water.
In addition, warm northeasterly winds pushed warm water toward the country from the sub-tropics, he said.
It had extraordinary impacts on Wellington, which recorded 17 days above 25degC this summer (the average is two), and Auckland had 47 days above 25degC (the average is 29) - the highest since records began at Auckland Airport in 1966.
Niwa principal climate scientist Dr Brett Mullan said the record books showed the previous hottest summer on record (1934/35) was so unusual, it prompted New Zealand Meteorological Service director Dr Edward Kidson to report on it in a special Meteorological Office Note.
The note showed there were several similarities to this summer, including widespread drought from November to mid-February.
''A feature of the pressure distribution was that the high pressure belt and tracks of moving anticyclones were unusually far south in the New Zealand area, generally crossing the Dominion instead of passing to the north of it,'' Dr Kidson's note said.
Dr Mullan said the persistence of anticyclones and north-easterly winds were also a feature of this summer.
Over land, Dr Kidson noted that ''in none of the four months November [1934] to February [1935] did any station in New Zealand record a mean temperature which was not above normal''.
