KEY POINTS:
Surface sea temperatures in December were the third coldest on record for the month, confirming the suspicions of summer holidaymakers.
National Institute of Water and Atmospheric Research records for December show surface sea temperatures were on the whole, 0.8C below the monthly average. Around the upper North Island, sea temperatures were between 1C and 2C cooler.
Since satellite measurements began in 1980, there have been only two instances where sea temperatures have been cooler than normal.
In December 2004, the temperatures were on average 1C cooler, and in 1982-83 there was a strong El Nino phenomenon, which saw sea surface temperatures drop by 1.3C.
While the average sea surface temperature for December was between 13C and 14C, there were huge variances between areas.
"The single number by itself is not necessarily so useful, depending on whether you're in Invercargill or the Bay of Islands," said Niwa oceanographer Phil Sutton.
Dr Sutton said the El Nino phenomenon was a contributing factor.
A strong El Nino dominated in 1982-83, the cooling in December 2004 took place during the end of an El Nino and the country was in El Nino at the moment.
"When we have El Ninos around New Zealand we tend to have cold oceans."
The weather phenomenon is partly responsible, but the mechanisms behind cooling oceans were still not fully understood, Dr Sutton said.
"Some of it's just the fact that with El Nino, you tend to get more southwesterly winds and southwesterly winds tend to be cold.
"So you get a little bit of direct cooling, but that's certainly not the whole story.
"People always have high expectations of December, especially since winter's been so awful, whereas in fact, the warm conditions really happen in February."
The peak of summer would still likely be cooler than normal.
"It will get better by February, but it will probably still lag behind a warm February," Dr Sutton said.
But an upside to the cool water was that the customary summer algal blooms, which can leave coastlines and beaches awash with red goo, might not happen," he said.
"Algal blooms tend to come when there's a thin layer of warm water at the surface.
"You could still get caught out - we could have one really calm warm week where a thin layer forms quite quickly from no wind and having a lot of sunlight.
"Odds are it might be better, but you couldn't guarantee it," he said.
But colder seas don't augur well for marlin fishing.
Harvie Ferguson, president of the Whangarei Deep Sea Anglers Club, based at Tutukaka, said marlin were temperature-sensitive fish that shunned colder waters.
The first marlin were usually caught just before Christmas, but this season none were hooked in the Bay of Islands until the new year.
"We certainly haven't caught one down this end of the world at this stage.
"They've been seen, but not caught."
Niwa principal scientist Jim Salinger said New Zealand was not alone in experiencing cooler waters. The sea around parts of Australia, such as the Queensland coast, was also cooling down.
Tourists the saving grace of sleepy, rain-lashed Auckland City
Queen St at lunchtime is usually so busy that pedestrians get swept along in the flow of shoppers.
But the annual post-Christmas exodus from inner Auckland combined with the cold and rain left footpaths empty yesterday and some retailers were feeling the pinch.
At Valentino's Gelato in the Ferry Building downtown, Erena Sawada said sales of gelato and sorbet had plummeted during the bad weather.
The shop was so quiet yesterday that she spent the day cleaning, in stark contrast to fine days.
"You should see this place on a sunny day, it's packed," said Ms Sawada. "Your wrist hurts [from rolling gelato]."
Further up the road at the Sunglass Hut, international tourists saved what would have been a dull sales day.
Assistant manager Meredith Matthews said visitors from Brazil, Canada and Sweden bought up sunglasses despite the lack of sun.
"Queen St isn't as bustling as it used to be," said Mr Matthews.
"It will pick up next week when the sun comes and more people return to work."
A souvenir shop owner also said overseas tourists continued to spend.
"We deal with overseas people who are here regardless of whether the weather is bad or not."
The shop was building up to March and April, its busiest months.
Heart of the City chief executive Alex Swney said retail sales figures for the last few weeks were yet to be processed but he had been told the performance was strong.
Mr Swney said a trend of workers taking shorter holidays after Christmas with a view to holidaying later was emerging. "We are less and less confusing Christmas with summer."
- Martha McKenzie-Minifie
Better weather everywhere bar Auckland
Think the summer's been terrible so far? Herald correspondents around the country say it's a different picture if you step outside Auckland.
MANGONUI, FAR NORTH
Tony Gee, Herald Far North correspondent
"It's been a great summer so far - very dry and hot, and people have long since run short of water. There's also an open fire ban that's been in place since just before Christmas.
"Temperatures have been down a little on usual summers, in about the low 20Cs. Monday was the first overcast day and Tuesday brought some welcome rain in the morning but it had stopped by about 11am and the sun was trying to come out again."
PAUANUI, COROMANDEL
Grant Bradley, Herald deputy news editor
"People were hunkered down Tuesday with driving rain and a large swell. But it was the first bad day after a glorious weekend, with temperatures around 25C and about 1000 people at the beach with the kids building sandcastles.
"There was no surf, just beautiful flat water. It wasn't great fishing but the sea temperature was up. A north-easterly began blowing Monday bringing cloudy periods but it was still warm."
NEW PLYMOUTH
Jon Stokes, Herald Central North Island reporter
"It's been pretty good since the weekend, though we've had a little bit of drizzle Tuesday. Monday was still nice after a weekend of beach weather but it's a bit grey and overcast today [Tuesday]."
WELLINGTON
Derek Cheng, Herald Wellington reporter
"The end of last week was beautiful and it carried over into a hot, sunny weekend. But clouds that were hanging off the hills since Monday meant it was cloudy with sunny patches, until they moved over the city on Tuesday. It started drizzling mid-afternoon and the wind picked up a little but it's not cold."
CHRISTCHURCH
Jarrod Booker, Herald South Island reporter
"Since the New Year, it's been a lot better than December. It's been a lot warmer though conditions have often been overcast.
"There's not been much in the way of rain in the last week. It's been reasonably dry and warm but overcast most of the time.
"It's not been especially hot but certainly warm and with warm winds from the west. It's pleasant today [Tuesday] and the temperature is up to 23C but overcast again."
GREYMOUTH
Jeanette O'Shea, freelance journalist
"It's lovely and warm down here and has been for the past few days. Tuesday has been a little overcast and there's been a bit of misty rain around but it's still warm."
