They had 690 hours of sunshine - a third more than they usually received - the National Institute of Water and Atmospheric Research's summer climate summary said.
Climate scientist Georgina Griffiths said it was a "topsy turvy" summer, starting out as extremely cold, with record cold temperatures in December, and finishing hot, with heat waves and above average temperatures in February.
Overall, it was an El Nino summer characterised by more "highs" in the Tasman Sea and over northern New Zealand, resulting in stronger than normal southwest winds over the country, she said.
While summer temperatures were above average in much of the North Island and western areas of the South Island, below average temperatures were recorded in eastern Otago.
"Morning temperatures in Dunedin this summer were the lowest on record," Ms Griffiths said.
Dunedin airport recorded 8.1degC (-0.8), its lowest mean minimum daily summer air temperature since records began in 1947.
The city was also the coolest of New Zealand's six main centres, recording an average 14.5degC (-0.2degC of normal).
It received 67% of its normal rainfall at 145mm, compared with Christchurch's 90mm, and 118% of its normal sunshine with 591 hours, similar to Christchurch's 592 hours.
While Balclutha was sunny, it was also cool, with the Telford station recording its third lowest summer mean maximum daily temperature of 18.3degC (-1.4degC of normal).
The cool December broke extreme daily maximum temperature records in Otago on December 2 with Oamaru only reaching 10degC (the lowest temperature for the period since records began), Dunedin airport 11degC (fourth lowest) and Balclutha 11degC (third lowest).
Dunedin also recorded its lowest extreme daily minimum temperature on December4 with -0.7degC.
Thunderstorm activity on January 21 produced very intense rainfall affecting Ida Valley in Central Otago.
It broke extreme one-day rainfall records, with Ettrick receiving 56mm and Alexandra 39mm.
Lauder received its second highest rainfall for a one-day event at 64mm and Cromwell its fourth highest at 48mm.
