The weather forecast showed wet weather clearing during New Year's Eve over the North Island and rain moving up the West Coast of the South Island.
Gusty northwesterlies were predicted for central New Zealand, including Wellington.
However, despite the potential change in weather, most main centres still looked fairly dry at this early stage, Mr Duncan said.
"Don't go cancelling any plans just yet."
Auckland has a 30 per cent chance of showers with westerlies picking up. New Year's Day could be windy but dry and cloudy.
Wellington is expected to be dry with near gale northerly or northwesterly winds on New Year's Eve - with New Year's Day looking similar but possibly showery.
Christchurch is forecast to be dry and warm, but perhaps cooler, cloudier and windier on January 1.
Mr Duncan said he had been using the same models that picked Cyclone Evan's path two weeks in advance.
"I tend to be a glass-half-full kinda guy and while the forecast may not be ideal, keep in mind long-range predictions are just a basic guide for the weather pattern.
"We are seeing another unsettled spell of weather, but it may be more like a hot spring weather pattern than the tropical summer system we've just had."
The wild weather may be be short-lived, a forecast high moving in to settle things down for the start of January.
WeatherWatch New Year's Eve predictions:
Auckland 30 per cent chance of showers with westerlies picking up.
New Year's Day could be windy but dry and cloudy.
Wellington Dry with near gale northerly or northwesterly winds. New Year's Day is looking similar but with a higher risk of showers.
Christchurch Dry and warm but possibly cooler, cloudier and windier on January 1.
