The first 10 months of this year have been 1C warmer than normal in New Zealand, according to data collected from seven spots around the country.
And the trend is set to continue, as Dr Brett Mullan, principal climate scientist at Niwa, is predicting warmer-than-average temperatures in November and December.
"We expect it to be very warm next week and summer to be above average, but not sizzling."
The current hottest year - 1998 - was 0.9C warmer than average in the 10 months to October and 0.8C hotter overall.
Mr Mullan said there were two reasons 2016 had been so hot in New Zealand - a rise in global temperatures and more northerlies.
Higher temperatures in New Zealand mirrored a global trend upwards and this year temperatures around the world would "probably hit the record books".
Winds from the north brought air in from the subtropics and in 2016 there had been an abundance of northerly patterns, he said.
Metservice forecasted more northerlies and temperatures in the high teens and low twenties for New Zealand's main centres this weekend, ahead of Guy Fawkes celebrations.
"Everyone wants the perfect clear skies. They will not get but it should be dry," meteorologist April Clark said.
According to the Niwa data, every month this year apart from August had seen warmer temperatures than usual, and February was particularly hot at 2C above average.
However, because of global warming, Mullan said it was unlikely 2016's record would last long.
"It's a guide that we're headed upwards."
He predicted higher temperatures would be felt in New Zealand within 10 years and globally even more quickly because they were measured over a larger area.
Warmer temperatures could affect horticulture postively or negatively depending on the level of rain, Mullan said.
He told the Herald kiwifruit orchards may need to be moved further south in future, because the plant needed winter frosts.
