Tropical Cyclone Gita is edging closer to New Zealand bringing potential power cuts, road closures, flooding and wind damage next week.

The Fiji Metservice upgraded the storm to Category 5 - the highest on the scale - this morning as it travelled over warm ocean waters 1800km north of Auckland.

Winds are sustained at well over 200km/h with gusts over 250km/h, and may reach 280km/h if it strengthens further today.

Weatherwatch NZ said the system could arrive Tuesday or Wednesday next week in western New Zealand.

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Although it would weaken slowly as it passed over the cooler waters in the Tasman Sea, it could still be equal to a Category 2 cyclone when it made landfall in New Zealand.

"Models suggest it will make landfall into the west coast of the North Island as an extra-tropical cyclone in the middle of next week, although there is still large uncertainty about the timing and intensity," a Weatherwatch NZ spokesman said.

"The most intense part of this cyclone is smaller than the North Island, so it's precise intensity and tracking makes all the difference on which parts of New Zealand will be worst affected, however it does appear it will come into the western side of the North Island or perhaps the Cook Strait area.

"Power cuts, road closures, flooding and wind damage are possible in New Zealand next week."

The spokesman also warned of dangerous seas around northern New Zealand from late Sunday.

Gita is tracking on an anticlockwise curve under Fiji, passing the southeast of southern Vanuatu and New Caledonia in the next few days and then heading south into the Tasman Sea, passing west of Norfolk Island.

MetService lead meteorologist Michael Martens this morning said even a weaker Gita would still bring strong winds and heavy rain if it hit New Zealand.

"I recommend people to keep an eye on the forecast especially over the weekend."

The intense cloak of humidity over the North Island is to continue for at least another day, although it has lessened in the South Island.

"In the North Island there is still a 20C-22C dew point - the temperature where it reaches 100 per cent humidity," Martens said.

"That is still what you would expect in the tropical islands."

The northern parts of the island have experienced heavy downpours, with as much as 91.5mm of rain falling in Northland from midnight yesterday, and an average of 40mm to 80mm across the region.

The deluge caused a landslip on State Highway 11 in Paihia, Northland, about 7pm, closing the road.

Detours via State Highway 1, 10 and 11 were in place.

Parts of eastern Bay of Plenty were flooded over the past few days, with as much as 300mm falling from Sunday to yesterday.

Heavy rain also fell in parts of Auckland, causing isolated flooding.

Niwa reported yesterday the organisation's climate centre on Auckland's North Shore had recorded 434.6 mm of rain so far this year.

This equated to 36 per cent of the normal annual amount, in just 12 per cent of the year.

Martens said the downpours had mostly subsided, but showers would develop again from Taupo north today.

There is some light relief for the weekend though, as a ridge coming through tomorrow brings fine weather for most of the North Island.

"That will provide some relief for the north over the weekend; time for a clean-up and to dry things out."

Enjoy it while it lasts is the message though, as another band of tropical air is forecast to arrive on Monday and Tuesday as Tropical Cyclone Gita comes closer.

A mainly sunny day is forecast for the South Island's West Coast after morning cloud breaks away, and drizzle is expected at times from Banks Peninsula southwards in the east.

Sunnier weather is expected further north in the east, with cloud and a risk of drizzle pushing northwards in the evening.

The weather will be mostly settled in the south over the weekend, after a small front on the West Coast will bring some rain on Friday.

Today's weather forecast

Occasional rain, chance heavy from afternoon, easing overnight. Light winds. 19C-27C

Auckland: Occasional rain, heavy at times, clearing overnight. Light winds. 18C-26C

Hamilton: Occasional rain, heavy at times, clearing overnight. Light winds. 13C-25C

Tauranga: Occasional rain, heavy at times, easing overnight. Northerlies.17C-25C

New Plymouth: A few showers, clearing evening. Light winds. 13C-25C

Napier: Occasional rain, chance heavy, clearing late evening. Light winds. 16C-26C

Wellington: Often fine with northerlies. 15C-23C

Nelson: Fine with light winds and sea breezes. 14C-25C

Christchurch: Cloudy with occasional drizzle. Afternoon fine breaks. Southeast tending northeast afternoon. 14C-22C

Dunedin: Cloudy with occasional drizzle. Afternoon fine breaks. Southerlies tending northeast in the afternoon. 14C-19C