Griffiths said January 2016 was "very warm", while its 2017 counterpart has so "run rather cool", and has been "very wet for much of the South Island and central New Zealand".
The average temperature for Auckland has dropped over 1C compared with summer last year, from 19.7C to 18.6C.
Wellington has gone from 16.3C to 15.4C, while Christchurch is slightly lower than last year, from 16.1C to 15.9C.
The months leading into the new year were also contrasting.
December 2015 was very dry and sunny, while December 2016 was warm early before hitting a colder-than-usual spell from the middle of the month.
Looking at summer so far, Griffiths said there had been "a lot of lows and fronts over New Zealand".
It had also been "very cold, especially the further south you go", she said.
It's been "windy, [with] frequent strong westerlies" and there has been "high pressure hanging in over Cape Reinga" with drier than normal conditions for Northland, Auckland and Coromandel.
The West Coast has lived up to its reputation by being "very wet", while it has been rainy and blustery for the South Island, Wellington and Wairarapa.
With eight days of January remaining, sunshine hours for Auckland for this month and last are at 374 hours so far, compared with 429 for last year.
Christchurch has had 338 hours of basking in the sunshine for the same period, compared with 402 last year.
Griffiths said Wellingtonians in particular will be noticing a lack of sunshine.
"It's been a very dull start to summer."
Griffiths said this year's summer "winners" have been Northland and Coromandel, who have had drier and sunnier weather than most of the country.
Last summer there were highs over the Tasman Sea and New Zealand, which brought with them unusually warm temperatures in January, with frequent northerly winds.
There were also high pressure systems over central New Zealand and the South Island, leading to a drier-than-normal season for those areas.
It was also wetter than usual for the Far North last summer.
This summer's rainfall in the main centres is mostly down compared with last year.
In Auckland, rainfall for December 2015/January 2016 was 155mm, while so far this year it has been 65.2mm.
In Christchurch it has dropped from 141.6mm to 103.6mm, while Wellington has a slight increase from 131.6mm last year to 134mm.
Griffiths said two large significant lows have affected the country in the last week, leading to the stormy conditions that battered New Zealand over the weekend.
"Looking ahead, the cooler southwesterly winds look likely to continue through the first half of February. However, it looks like the lows and fronts that come across New Zealand are weaker, with less vigour, than what we have seen lately.
"The good news is that we should have some windows of better weather in the first half of February for that beach trip or the barbecue."
She said the upcoming Auckland Anniversary Weekend looks like it will "remain a touch on the cool, breezy side, but with some doses of sunshine, too".
"Once we hit the middle of February, we are going to have to keep an eye on the tropics. It has been very quiet up there, but this will not last."
