State Highway One between Peketa and Goose Bay has been closed all weekend after heavy rain caused debris to fall over the road.
New Zealand Transport Agency Regional Performance Manager Pete Connors said it wouldn't be accessible unless the rain stopped soon.
"While it continues to rain, there's going to be debris coming down but once it stops we hope to have it open pretty rapidly."
He urged drivers travelling to or from Kaikoura to use Route 70 via Waiau and to check the road travel map on the NZTA website.