It's the first day of winter and it seems the country is in for a mixed bag of weather this season.
NIWA is predicting a turbulent start to the winter months with June bringing heavy rainfall, snow and strong winds, before the weather settles with drier conditions in the east.
Issued on Thursday, NIWA's seasonal climate outlook said winter will unlikely be colder than average but is predicting it will be colder than recent winters which had record-breaking warm temperatures. This is because marine heatwave conditions persist in New Zealand's coastal waters, particularly near the South Island.
El Niño, a naturally occurring global climate cycle known as the El Niño Southern Oscillation, is predicted to continue to develop during winter and be a potentially strong event by spring, NIWA said.
For New Zealand, during the winter it tends to bring winds from the south, causing colder temperatures across the summer. El Niño also increases the chances of more frequent and extreme adverse weather events.
The seasonal climate outlook report said there is a 90 percent chance of El Niño developing by August/October with around a 70 percent chance of it continuing through summer.
It comes after La Niña, the opposite phase of the global climate cycle, stuck around in New Zealand for three consecutive years, finally coming to an end in March.
Despite a trend towards El Niño, NIWA said warmer-than-average sea temperatures remain present in the western Pacific, which is expected to bring heavy rainfall, snow and strong winds through June.
While June is expected to be particularly wet, for the whole winter season, NIWA said rainfall is most likely to be near normal in the west of the North Island, and the west and north of the South Island. In the east of both islands, rainfall is likely to be at or below normal levels.
"While a transition to El Niño is occurring, the persistence of warmer than average ocean water in the western Pacific, a La Niña-like tendency, is supporting and will continue to support an increased frequency of low-pressure systems around New Zealand," NIWA said.
"Some of these disturbances will come with sub-tropical and/or tropical moisture. El Niño-like patterns may develop during July and/or August, allowing for periods of time with less rain, particularly in the north and east of both islands."
The news may come as a relief for the northern and eastern parts of the North Island which saw an extremely wet start to the year with flooding, cyclones and record-breaking rainfall.
