NIWA says this summer is the sunniest on record.
The National Institute of Water and Atmospheric research says the last three months have been characterised by plenty of sunshine and just a smattering of rain.
However, the temperatures have not broken any records.
Tauranga and Auckland had the highest average temperatures at 19.7 degrees Celsius.
Wellington's average temperature was 16.9C - one degree higher than normal - and Christchurch was 17.1C.
NIWA climate scientist Georgina Griffiths said anticyclones sitting over New Zealand blocked the wet weather.
The highest temperature was 35.1C recorded in Clyde in Central Otago on 5 January and also in Gisborne on 9 and 10 January.