A southerly blast sweeping up the South Island is due to bring severe gales and has forced the cancellation of tomorrow's Interislander ferry sailings.
MetService warned of southwest gales gusting up to 120 km/h in coastal parts of Southland, Clutha and Dunedin, especially from Bluff around to the Otago Peninsula, Nelson west of Riwaka, Banks Peninsula and the Port Hills of Christchurch.
In the North Island, severe northerlies were expected in Wairarapa and Hawke's Bay south of Hastings from this afternoon through to the early hours of tomorrow, gusting 120 km/h in exposed places.
The bad weather has forced the Interislander to cancel tomorrow's Wellington-Picton ferry sailings with swells of up to eight metres forecast in Cook Strait.
The last sailings until Thursday will be tonight's 8.30pm service from Wellington and the 10.15pm from Picton.
The Interislander expected to resume at 6.30am on Thursday, while Bluebridge said passenger services would resume at midday on Thursday.
Bluebridge said its freight service would go ahead tomorrow morning, although the afternoon and evening sailings have been cancelled.
Otago's electricity network company Aurora Energy said the wind could bring down trees and power lines and urged people to be ready for the possibility of power outages.
The Transport Agency warned drivers to be extra vigilant in the South Island, with the wintry blast expected to continue to affect roads and driving conditions in many areas over the next two days.
State Highway 87 (Outram to Kyeburn) in Otago, is closed to all non-four wheel drive vehicles due to snow.
It is also snowing snowing on the Crown Range Road, between Wanaka and Queenstown, and chains must be fitted.
A Transport Agency manager, Lee Wright, asked for drivers to keep their speeds down, especially on gritted roads.
Motorists should be prepared for very cold weather, Ms Wright said, especially if the were travelling the alpine passes such as SH73 Arthur's Pass, SH7 Lewis Pass, and SH8 Lindis Pass, as conditions could change quickly and catch people out.