Air NZ flights have been cancelled in and out of Christchurch, thousands of homes are without power and roads are closed as a storm dumped snow on New Brighton beach and brought good cheer to skiers.

About 3000 customers were without power late on Wednesday, Orion Energy said.

Christchurch Airport remained open but many airlines cancelled flights.

The situation will be reviewed on Thursday morning when ice may be a problem.

"What I understand happened last time was ... the second day was pretty tricky when things iced over," airport spokeswoman Yvonne Densem told NZ Newswire.

She said an Emirates flight departed on Wednesday night.

"Snow is still falling heavily across the Orion area in Christchurch and central Canterbury. It appears that the cold front has stalled over Christchurch and the area inland," Orion chief executive Rob Jamieson said late afternoon.

"It's likely that some people will be without power overnight," he said.

Power is also out to residents in parts of Kaikoura in north Canterbury.

About 10 people were evacuated from two homes in Coal Creek near Greymouth on the West Coast, and a resident of Ruby Bay near Nelson moved when sea water inundated their section.

Emergency services in Nelson and Tasman reported trees down and surface flooding but said river levels are now dropping.

Snow will continue to fall and road closures are likely into Thursday in Nelson and Tasman.

A number of alpine roads, including the Lewis Pass, Porters Pass and State Highway 73 through Arthur's Pass were closed for part of the day.

But skiers are happy.

"The perfect storm has arrived with 40cm of fresh snow falling on the base area and 50cm on the summit," Mount Hutt, the largest field in the region, reported ahead of its opening on Saturday.

An update said: "70cm new snow, still snowing".

Chris Haines, St John regional operations manager in Canterbury, said people needed to be careful in the evening as driving and walking conditions were difficult.