State Highway 6 into Makarora at the northern end of Lake Wanaka has been closed for Monday night because of the danger posed by a large slip.
The Transport Agency wants to try to stabilise an estimated 5000 tonnes of rockfall.
The agency's Central Otago area manager, John Jarvis, says heavy rain has exposed further debris at the highest point of the slip about 100 metres above the highway, making it unsafe for motorists to use the road at night.
Mr Jarvis says the volatile weather and steep terrain are creating a challenging environment for contractors, and it'll be several weeks before the road is fully operational.
The closure is from 7pm until 7am on Tuesday.