Unpredictable Cyclone Gita could hit anywhere in New Zealand

Cyclone Gita's path is so unpredictable it's impossible to know where in New Zealand will be hit, but one thing's for sure - the "high impact" cyclone will hit somewhere, forecasters say.

The monster tropical cyclone is looming near New Caledonia after crashing through Tonga on Monday night, leaving thousands of homes flattened and entire islands cut off.

MetService meteorologist Claire Flynn told Newshub the storm is evolving as it moves down.

"When you're up in the tropics it's a tropical cyclone, which means there's an eye of the storm - and the strongest winds are closest to eye.

"But it will transform into a mid-latitude cyclone as it comes south. The strongest winds can cover a much broader area. It can be much more widespread."

Ms Flynn was careful not to predict specifics - saying the highest wind speeds and rainfall cannot yet be ascertained - but says the whole country should be ready to bunker down if necessary.

"The size of any impact will be highly dependent on where it hits."

The storm is still "well up in the tropics", but will curve around New Caledonia and towards the country on Friday night, hitting next Tuesday.

Gita is currently a category 3 storm, but as it evolves, it will lose any category status.

That doesn't mean it won't be a serious storm, Ms Flynn adds. Mid-latitudes simply aren't measured by categories - instead by the speed of their winds and rainfall.

There is an unrelated severe weather warning for the West Coast on Friday and a weather watch on Canterbury High Country with heavy rain expected - but if you're in the upper part of the country, forecast for warm and calm conditions over the weekend, best make the most of it.