State Highway 6 between the Gates of Haast Bridge and Haast Pass Summit will reopen at 2pm.
The NZ Transport Agency said today the road would only be open between 8am to 6pm for the foreseeable future.
A large slip at Diana Falls has kept the highway closed since 8pm on Tuesday, September 10.
Agency West Coast area manager Mark Pinner said today's opening was dependent on the weather.
About 15mm of rain fell in the area overnight, pushing the planned midday opening out by a couple of hours.
"We expect only one lane of the highway will be available for some time. Our ongoing challenge with managing the site is that the slip face hasn't settled completely.," he said.
"Today's rain shows just how easily the slip can be reactivated."
