Last year was Aotearoa's warmest year on record according to Niwa's annual climate summary - passing the previous record set in 2016.

Niwa says there were no months that experienced below average temperatures during 2021. 

The nationwide average temperature was 13.6C; that is 0.95C above the annual average set between 1981 and 2010.

Niwa climate scientist Nava Fedaeff said the winter of 2021 was also the warmest one on record, beating the previous record set in 2020.

"2016 recorded an average temperature of 13.45 degrees or 0.84 degrees above average which was New Zealand's warmest year on record at the time," Fedaeff said.

"However, in 2021 we finished with an average temperature of 13.56 degrees which was 0.95 degrees above average and became New Zealand's new warmest year on record."

Auckland, Bay of Plenty, Tasman and Fiordland had temperatures well above the average while Taranaki saw the most sunshine hours.

Ashburton recorded the highest temperature for the year - 39.4 degrees on 26 January.

Fedaeff said the trend was consistent with global warming patterns.

"Seven of the past nine years have been amongst New Zealand's warmest on record," she said.

June and November were warmer than ever and temperatures peaked above average in most other months, Fedaeff said.

"Three months of 2021 featured what we consider near average temperatures, which is within half a degree of average and that was January, February and September.

"A relatively cool start to the year, obviously this was summer, but for the time of year it was cooler compared to the rest of the months of the year when in fact the remaining nine months of the year featured above average temperatures.

"During 2021, there were no months that experienced below average temperatures."

Fedaeff said there were regional differences when looking at the breakdown of temperatures across the country, but it was to be expected.

She said 55 percent of days experienced above average or well above average temperatures - at least half a degree higher than the average.

"No matter what way you slice it, be it year, month or daily data we can see that we had quite a lot of warmth during 2021."

She said it was the warmest year on record for 12 locations and a further 50 experienced annual average temperatures in the top four warmest on record.