Tropical Cyclone Hola is moving slowly past Vanuatu as it becomes increasingly likely the storm will hit New Zealand on Sunday or Monday.

The Category 2 cyclone is expected to strengthen through the morning and reach Category 3 over the next 12 hours.

Three forecasting models for tropical Cyclone Hola predict the storm is likely to hit New Zealand's North Island early next week.

Two models, from the UK Met Office, show Hola could hit the Bay of Plenty on Monday. It would be the third cyclone this season to affect New Zealand.

The third model, from the European Centre for Medium-Range Weather Forecasts, predicts it could make landfall about 6pm on Monday.

Metservice New Zealand lead meteorologist Mark Todd said computer models were still struggling to give an accurate track but it was looking increasingly likely the storm would affect New Zealand.

Hola has been moving slowly over Vanuatu during the past 24 hours, and reports say gale-force winds collapsing some houses.

The roof of a classroom was blown off and some houses collapsed on Vanuatu's island of Ambrym as the cyclone arrived this afternoon, Radio New Zealand reported.

Todd said it was west of Vanuatu this morning, and moving slowly further west.

"We expect over the next day it should start to recurve to the south/southeast, in the general direction of New Zealand.

"If we are lucky it will pass just to the north of us. If we are unlucky, it could be a direct hit into the North Island.

"By then it will become an extra-tropical system, as always happens, but if it does make a direct hit there will be heavy rain and high winds."

A "cut-off low" west of New Zealand has been wreaking havoc as it moves slowly over the North Island.

"We have a deep low in the upper atmosphere and a deep low at the surface generating all the rain and wind," Todd said.

Heavy rain and thunderstorms rocked much of the island last night with up to 200mm falling in places.

Wairarapa, Tararua and Hawke's Bay south of Hastings have a severe rain warning in place through to 9pm tonight.

Heavy rain warnings remain in place for Taranaki through to 1pm.

"The heaviest falls were in the central areas, from Hawke's Bay and the Wairarapa through the central high country to Taranaki," Todd said.

More than 200mm was recorded on Mt Taranaki, and 129mm in nearby Stratford during the last 24 hours.

On the East Coast 90mm fell at Castlepoint in the Wairarapa and 83mm in Taumarunui.

The lower North Island including Wellington has been experiencing gale-force winds.

"These are not expected to ease off," Todd said.

"There will be a gradual trend off, as the weather system moves very slowly.

"There is a risk of more widespread thunderstorms today, mainly in the central and upper North Island, even some hail."

Temperature-wise today would be much the same as yesterday, with the South Island "the place to be", Todd said.

"There is a somewhat cooler air mass over the South Island, but it is going to be sunny, with very little rain."

Today's weather

Auckland - Fine spells and occasional showers, possibly heavy with thunderstorms. Northeasterly turning southeast. 23degC high, 17degC overnight.

Hamilton - Occasional showers, possibly heavy with thunderstorms from afternoon. Southeasterlies. 25degC high, 14degC overnight.

Tauranga - Fine spells and occasional showers, possibly heavy with thunderstorms from afternoon. Light winds. 24degC high, 17degC overnight.

Wellington​  - Occasional rain. Strong southerlies. 17degC high, 13degC overnight.

Christchurch -  Some morning cloud then fine, but chance shower. Cloud increasing evening. Southeast breezes developing. 18degC high, 12degC overnight.

Dunedin -​ Morning and evening cloud, afternoon fine spells. Southwest developing afternoon. 17degC high, 11degC overnight.