Civil defence authorities are warning North Islanders to brace themselves for a storm which could wreak havoc overnight.

Power outages, airport closures and wave surges could be expected when gale-force winds and heavy rain start showing their teeth around midnight, the Ministry of Civil Defence and Emergency Management said in a statement.

"The only good thing about the forecasted front is that it is expected to pass through quickly. But we can expect it to pack a punch,'' said the ministry's civil defence director John Hamilton.

People in the whole of the North Island - especially the central and southern parts - were advised to plan for power outages, affected water supplies and broken windows.


Wind damage and wave surges were also likely to affect roads.

Interislander ferry sailings scheduled for after 6.25pm today have been cancelled as a result of the anticipated storm.

Acting general manager Ross Allen said that, weather permitting, they would resume sailings on Sunday morning.

Weatherwatch analyst Philip Duncan said winds were now predicted to be stronger than initially forecast for much of the country, with gusts of up to 150km/h predicted for many rural and coastal areas.

"We had initially thought the wind and rain would be about equal. Now with the wind forecast picking up it looks as though it'll be this jetstream that will just zip past very quickly and some places may only end up with showers.''

The fast and furious storm should last less than 24 hours across the country, with some places in the clear after just six hours of rough weather.

Preparations are also being made in case the severe weather stirs things up around the wreck of the stricken cargo ship Rena off Tauranga.

Winds gusting up to 50 knots and swells of over 5m are forecast for tomorrow.


Salvage company Svitzer has brought the barge Smit Borneo and other support vessels into port as a precaution.

Organisers of major weekend events, including Derby Day at Ellerslie Racecourse in Auckland and the Black Caps' final one-day international against South Africa, at Eden Park have been preparing for the worst.

With luck, the Warriors' grand final rematch against the Sea Eagles on Sunday afternoon will be safe because the skies are predicted to clear by then.

The Sounds in the Sun event, which was to be held at Unitec's Mt Albert campus tomorrow, has been relocated to Vector Arena. Up to 10,000 people are expected at the day-long concert to hear performers such as Shapeshifter, Katchafire and Kidz in Space.

Ironman New Zealand organisers have called off the event, scheduled for tomorrow at Taupo and instead a half-ironman will be held on Sunday, weather permitting. About 1600 competitors had entered the event, which had been sold out.

Vector chief executive Simon Mackenzie said crews have been put on alert and all efforts would be made to respond to power outages as soon as possible.

The Fire Service is also bringing on extra staff in anticipation of a large number of weather-related incidents overnight, a spokeswoman said.

The Ministry of Civil Defence and Emergency Management advises that people:

* Secure, or move indoors, all items that could get blown about and cause harm in strong winds, such as rubbish bins and outdoor furniture, trampolines

* Water supplies can be affected so it is a good idea to store drinking water in containers and fill bathtubs and sinks with water

* Check drains and spouting and clear any blockages

* During a storm, close windows, external and internal doors. Pull curtains and drapes over unprotected glass areas to prevent injury from shattered or flying glass

* If the wind becomes destructive, stay away from doors and windows and shelter further inside the house

* Don't walk around outside and avoid driving unless absolutely necessary

* If you are travelling keep up with updates and drive to the conditions

* Unplug small appliances which may be affected by electrical power surges. If power is lost unplug major appliances to reduce the power surge and possible damage when power is restored

* Bring pets inside. Move stock to shelter. If you have to evacuate, take your pets with you

* Report flooding to your local council