A slip has closed parts of State Highway 6 near Lake Moeraki on the West Coast of the South Island.
Severe weather is making its way across the coast after more than 50mm of rain fell in just two hours early on Wednesday.
Flooding is also affecting the highway between Hari Hari and Haast, with small slips causing debris to spill onto the road.
Authorities are urging motorists to be cautious and delay travel if they can.
The New Zealand Transport Agency say crews are working hard to get the highway reopened.
A front moving up the South Island is bringing heavy rain and thunderstorms but is expected to ease throughout the day.