Wellington's wild weather proved too much for a Bluebridge ferry that was forced to turn back before even making it out of the harbour.

Video footage sent to the Herald from a ship in the Cook Strait showed waves crashing over the side, and rolling towards the door of the vessel - forcing the person filming to quickly slam the door shut.

The ferry was one of the only ones which departed Wellington this morning, heading into forecast swells of up to 7 metres.

A spokesperson for the ferry told the Herald the boat left at 8.15am, hoping to make it out before the storm hit.

However the weather deteriorated faster than expected, and the ship returned to port before it made it out of the harbour.

The spokesperson said safety is the company's biggest priority and conditions in Cook Strait had deteriorated earlier than expected making it unsuitable to sail.

"We're sorry that this will inconvenience our customers, and we're working hard to get everyone across Cook Strait as soon as conditions allow."

Anyone who wished to cancel their sailing would be refunded.

It's been a wild morning for the capital with gale-force winds tearing off roofs and grounding all flights in or out of Wellington.

Several roads have been closed across the region, and hundreds of homes are without power as the storm rages on.

A heavy swell warning is in place for Wellington from Cape Terawhiti to Turakirae Head. Swells are expected to peak at 7m early this evening, and will be between 5m and 7m through tomorrow afternoon.

Wellington Regional Emergency Management is warning people to stay off the beaches and avoid driving on coastal roads during peak swells.

"Swells can cause surface flooding and debris wash up including driftwood, seaweed, sand and gravel."