Gales and stormy weather moving up the country cut power a wide area at the top of the South Island overnight and brought winds gusting to 120 km/h to the capital.

A heavy band of rain is approaching the North Island this morning.

Snow has fallen to 400 metres in many parts of the South Island, closing State Highway 94 to Milford Sound.

Fallen trees across State Highway 69 on the West Coast have closed the road, which is expected to re-open this morning. There are also fallen trees being reported in the Eastern Bay of Plenty.

Hand-drawn analysis, combined with the radar image, shows situation at 3am as low crossed the South Island. Lots of isobars=very windy! ^TA pic.twitter.com/ywCoq6A1Pw

— MetService (@MetService) November 7, 2017

Fire crews were called out to downed power lines, road blockages and flooding.

Southern communications acting shift manager Ian Littlejohn says widespread power outages affected the West Coast, the upper South Island and the east coast down into North Canterbury.

He says it was eventful between midnight and 3.30am, especially on the West Coast, where roads were closed, trees and power lines were down and there was flooding.

"Fire and Emergency attended approximately 14 events. They ranged from assisting with the evacuation of campers from a low lying campground in Mapua [near Nelson] through to securing loose roofing material, assisting members of the public with flooding caused by storm surging.

"As a whole we only received reports of one or two trampolines flying this time. Regrettably one of the trampolines went into a transformer station.

"The worst hit area would be the West Coast, which suffered a number of road closures due to storm damage and power lines down across the road.

"We're expecting another surge of calls as people wake to the damage."

Gales and downpours hit Wellington overnight, with wind gusts of 120km/h recorded at 1am at Mt Kaukau.

As the severe weather moved in, Christchurch had winds gusting to 100km/h, Hokitika had 95km/h wind and 90km/h gusts were recorded at Waiouru.

The storm is forecast to clear quickly this morning.

A cold front has also moved eastwards across the North Island.

Midnight isobar map shows low starting transition across South Island. Lots of lines = lots of wind. ^AG pic.twitter.com/Gx1KuyetmH

— MetService (@MetService) November 7, 2017