The cyclone that devastated Samoa and Fiji will deliver heavy rain and gales to the north of the North Island on Sunday and Monday, and could linger on to spoil Christmas.
The former Cyclone Evan will lie near Northland late on Sunday. Periods of heavy rain are forecast for Sunday and Monday in Northland, northern parts of Auckland, Coromandel Peninsula, western Bay of Plenty and northern Gisborne.
Winds in Northland and possibly Auckland are expected to be strong or gale northeasterlies.
MetService has issued a severe weather watch, and expects to put out a weather warning on Saturday.
People, especially holidaymakers and trampers, are urged to check the latest forecasts as there may be localised flooding and disruption to transport.
"Evan will bring a large amount of tropical air over New Zealand, which means the potential for heavy rainfall in places with strong onshore winds," chief forecaster Peter Kreft said.
"Christmas Day looks unsettled for many places."
By Christmas Evan will be over the Tasman Sea, maintaining a warm, humid northerly flow over much of the country.
The best place to be for Christmas Day looks like the east of the country between Wairarapa and Canterbury, as rain is also forecast for Nelson and the West Coast of the South Island.
While the weather will be unsettled on Christmas Day it should be warm and calm.
"So, Christmas dinner outside isn't completely off the table for everyone," said Mr Kreft.
Cyclone Evan displaced thousands of people in Samoa and Fiji and caused hundreds of millions of dollars worth of damage. Five people died in Samoa and others are still missing.
Auckland Mayor Len Brown said an Auckland relief committee was set up after he hosted a meeting of Pacific leaders on Friday.
"Auckland is the largest Pacific city in the world. Pacific Aucklanders have lost friends and family, and family and community property has been badly damaged. Auckland will do whatever it can to help as we identify the most effective way to assist."