Cyclone Gita could break a record by striking further south than any previous tropical cyclone, according to one forecaster.

The tropical cyclone is still classified a Category 3 as it moves through the Pacific, where it is expected to make a U-turn toward middle New Zealand.

Most of the North Island is due for a hot, humid Sunday as Gita pushes a rainband ahead of it.

But it's only the start, with the MetService warning of impending heavy rain and damaging winds when Gita arrives. The forecaster is warning people to prepare for Gita's arrival by tying down loose furniture and getting supplies ready.

The Category 3 tropical cyclone is expected to curve southeast late today or early on Monday and track toward us.

While the MetService predicted Gita will have lost its cyclone status by the time it arrives late on Tuesday, Weatherwatch predicted the cyclone could still be a Category 2.

WeatherWatch forecaster Philip Duncan said he had never seen such a southern tropical cyclone before, tweeting that it could break a record if it remained a tropical cyclone when it arrived in the 40th parallel.

Even as an ex-cyclone, Gita will still be a major storm according to the MetService. Heavy rain and severe gales mean there will likely be significant coastal damage, with waves up to 12m.

Heavy rain is expected from Waitomo down to the Lakes district, while severe gales are likely to hit the upper South Island and the West Coast, as well as Taranaki and Wellington.

There is a lower risk of severe gales for the rest of the North Island, excluding the East Cape.

The MetService issued its first official Gita forecast last night as the cyclone left Fiji MetService's warning area.

Gita has already cut a swathe through the Pacific, causing flooding in Samoa and devastation in Tonga where thousands of buildings have been destroyed.

Australians are being warned to stay out of the water along the coast of New South Wales as Cyclone Gita sends hazardous surf their way.

The cyclone has been tracking slightly further south than predicted, meaning the South Island could once again be in its path.

Christchurch and Dunedin are also in line for possible flooding, although it's hoped the worst of the weather will be broken up by the Southern Alps.