Christmas looks like being warm and sunny - but there's a spanner in the works, in the form of tropical Cyclone Evan.
The storm that has pounded Samoa and Fiji is making long-term predictions difficult for New Zealand forecasters.
John Law, of MetService, was unwilling to give an outlook for Christmas Day, and said the forecaster was running an "ensemble" of computer models to keep track of the cyclone.
However, MetService's website was offering a 10-day forecast that predicted sunshine and highs of 22 degrees Celsius for Wellington on Christmas Day and Boxing Day, with no rain.
Humid air and strong winds in the tail of Cyclone Evan could change the forecasts, Mr Law said. Northland and Auckland could feel its effects at the end of this week, but it was not clear how severe they would be.
"The track of the cyclone is going to turn, and we're going to try and get a bit more certainty," Mr Law said.
WeatherWatch head analyst Phillip Duncan agreed that the cyclone was a "wildcard" in what had otherwise been a settled forecast for central parts of the country on Christmas Day.
"Evan is, at this stage, not expected to negatively impact Wellington's weather on Christmas Day, but the unpredictable nature of tropical systems means it's the wildcard in our forecast.
"Without Evan in the picture, I'd say New Zealand has a 90 per cent chance of a sunny, hot, Christmas Day."
Fuelled by warm, moist atmospheric conditions, as the cyclone heads toward New Zealand its path and intensity will be dictated by the temperature of the water it crosses and the weather systems it encounters.
- Fairfax Media
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