An El Niño weather pattern may develop this year, a Niwa forecaster says.
During an El Niño , New Zealand tends to get stronger or more frequent winds from the west in summer, typically leading to drought in east coast areas and more rain in the west.
There was a strong El Niño in New Zealand two years ago, and a La Niña weather pattern has just ended. Even so, this summer, Northland and Hawke's Bay were hit by drought and farmers had to drop stock numbers and cull dairy herds because of feed shortages.
The National Institute for Water and Atmospheric Research (NIWA) said models predicted a more than 50 percent chance of a return to El Niño conditions from August to October.
Forecaster Chris Brandolino said sea temperatures had warmed off the South American coast, which could be stage one of a El Niño developing.
Some models were predicting an El Niño that would be moderate or higher, and that would be very unusual at this stage of the weather pattern. "So that's what is grabbing the attention of people."
The outlook summary from NIWA for March to May predicts average or above average temperatures in the north and east of both the North and South Island.
Rainfall for all regions, except the West Coast of the South Island, are likely to be near normal or below normal.