Wellington is being battered by a fierce storm, with material being turned into "missiles'' by the strong wind.

Wellington City Council said its call centre had received more than 200 calls this evening as the southerly storm hit the city and region.

It was aware of reports that a number of houses were losing roofs, windows were breaking and of other structural damage.

Acting Civil Defence controller Neville Brown said it was essential that people stay indoors if possible.

"There is a lot of material being turned into missiles it is a potentially lethal situation out there.''

Storm-force southerly winds had brought down trees and slips in many Wellington suburbs.

Middleton Road, between Johnsonville and Churton Park, had been closed after at least six big macrocarpa trees fell on to the road. One tree has fallen on a car.

Ohariu Valley is cut off from Wellington City by fallen trees blocking Ohariu Valley Road

Mr Brown said while the Council had crews out clearing roads and attending to as many trees as possible, conditions were treacherous and in many cases it would be too dangerous to carry out work.

If the storm conditions continued tomorrow, Mr Brown urged commuters to take extreme care if they headed to work.

"There are likely to be all sorts of obstructions all over the city and region. People should take it easy if they are driving.''

Driving conditions around the region are treacherous and motorists are urged to stay off the roads unless absolutely necessary.

Flights, ferries and trains in and out of the city have been halted and Fairfax reported that the interislander ferry Kaitaki had broken its mooring in 160km/h winds and had to be temporarily anchored in the harbour.

Swells of up to 10 metres have been reported in Cook Strait and with high tide expected at about 1am tomorrow, there are concerns about possible damage to property and roads along Wellington's south coast.

Diners ate in darkness on Wellington's waterfront after the storm cut power in parts of the city centre.

Wellingtonian Sue Jury said the lights went out just as she was ordering dinner at Portofino restaurant at 8.30pm.

"Still, it could be worse. One of the others had to go home because a tree went through their dining room window."

Ms Jury said it was the worst storm she had witnessed in 10 years in the capital.

Australian Bob Ritchie said he had only been in Wellington a few hours, and was already considering heading back to Brisbane.

"We're used to drought where I'm from. I think this is worse."

Further up the coast, huge swells broke over the seawall onto the city bound lanes of the motorway. Drivers slowed to 20km/h as sea spray shrouded all six lanes.

There are still multiple power outages around the region including Lower Hutt, Wainuiomata, Miramar, Johnsonville, Makara, Porirua, Titahi Bay and Whitby.

About 25,000 customers are without power and in some cases the power will be off until at least the morning.

The Wellington Regional Emergency Management Office opened its Thorndon headquarters this evening.

Wellington Region Civil Defence controller Bruce Pepperell said the office was mainly co-ordinating a very large number of "relatively minor" events around the region.

"The emergency services and council contractors are flat out dealing with fallen trees, flying roofing iron and other wind-related problems.

"We have opened to keep an overview of where the problems are and to direct resources where necessary. At the moment we are not considering any formal civil defence activation."

The Porirua and Hutt City Emergency Operations Centres had also opened.

- APNZ