A slip has closed part of State Highway 6 on the West Coast as heavy rain causes flooding, fallen trees and further slips across parts of the South Island.

NZ Transport Agency said SH6 Coast Road between Punakaiki and Fox River had been closed because of a slip at Meybille Bay.

Motorists were being asked to avoid the area or delay their journeys.

Flooding has also been reported on SH6 in the Lower Buller Gorge, on several parts of State Highway 7 between Greymouth and Reefton, and on SH7 and SH65 between the Hanmer Springs turnoff and Murchison.

Fallen trees have been reported on SH6 at Berlins and Inangahua Junction, along with State Highway 67 near Westport.

Further south, snowfall is affecting areas including Lindis Pass in Otago, with motorists being urged to take extra care.

MetService has an orange heavy rain warning in place for the Grey and Buller districts and Nelson Lakes until 1am Monday.

The warning means streams and rivers may rise rapidly, while surface flooding, slips and difficult driving conditions are possible.

Heavy rain watches are also in place for the Canterbury high country north of Aoraki Mount Cook, southwestern Marlborough and the ranges of Westland north of Mount Cook National Park.

Limited snowfall is possible on Porters Pass and Arthur’s Pass on State Highway 73, as well as Lewis Pass on SH7, through until Monday morning.