Forecaster Sarah Garlick said the long stretch of fine weather - Wellington is on track for 10 sunny days - was rare.
"It's a very large, slow-moving high and it's just at the right latitude to be right on us."
The high would slowly move to the east, and two weather systems at the southeast and northwest of New Zealand would bring more unsettled weather.
WeatherWatch.co.nz head analyst Philip Duncan said the high was the strongest of the summer.
"In New Zealand we're not used to the weather staying the same for more than a few days, so when you get sun for more than a week it's unusual.
"It's not quite fitting with being in the roaring forties and being on two small islands in the South Pacific."
The last seasonal outlook from the National Institute of Water and Atmospheric Research (Niwa) said January-March rainfall in Northland, Auckland, Waikato and the Bay of Plenty was likely to be in the near normal range. Temperatures were also likely to be near average.
Mr Duncan said models indicated a chance of rain around February 4, and again from February 7-9.
Next month, Auckland's weather would be more changeable, with some cloud and showers.
"But I don't see for northern New Zealand significant rain, unless this unsettled weather pattern that's predicted next Monday intensifies.
"For places in the east, like Hawkes Bay, there's very little in terms of rain coming up. Some places are going to get very, very dry."
Yesterday, the Fire Service continued to respond to fires including a suspicious blaze at Ranui and a bush fire at Whangarei Falls, in Northland.
Sun shines on holiday business owners
The stretch of sunshine has been a welcome relief for business owners who struggled during the wet of last summer.
Geoff Hawthorn, owner of the Dickson Holiday Park near Thames, said numbers this summer had improved significantly.
"The biggest thing is, everyone is way happier. People are having a lovely holiday this year. It's stunning.
"Everyone has gone to refill Auckland. I've just finished cleaning for the day, our park looks empty. I think Auckland must have been empty for the weekend."
Mr Hawthorn said last summer's constant rain was devastating, with people leaving early or cancelling holidays altogether.
"I think we went from close to 200 people to nine."
Go Fish Tackle owner Greg Hill said sales were much stronger compared with last summer.
His Northcote business sold to other stores, with those in popular holiday spots reporting particularly strong sales this season. "Our industry is weather-related ... We are certainly up from last year, definitely."
Craig Carter, chief executive of Community Leisure Management - which manages 21 pools nationwide including the Parnell Baths - said numbers were far better than last summer.
"We are doing okay. We haven't had rain - but if you look at the sunshine hours, we are pretty much in line with an average year."
Auckland has recorded 207.2 sunshine hours so far this month, just above the average year to date of 206 hours.
In comparison, Gisborne recorded 263.8 hours, compared with an average year to date of 209.
WeatherWatch.co.nz head analyst Philip Duncan said "average" in sunshine hours was good as far as holidaymakers were concerned.
Westerly winds on the east coast meant it had little cloud or rain, but the west coast was cloudy.
"Because it's been windy, the cloud breaks up, and we end up with sun and cloud. It's very rare in Auckland that you get a cloud-free day ... because it's such a coastal city."
- additional reporting: APNZ
