Glenorchy Road had been closed at Bob's Cove since Saturday morning due to an "impassable and dangerous" slip.
However, contractors had made "excellent progress" clearing it and diverting the culvert, the Queenstown Lakes District Council said.
The road, about 36km from Queenstown, had been closed since Saturday morning but re-opened late on Sunday afternoon.
However, there was a 30km/h speed limit through the affected area on the road as the surface was unsealed and uneven.
"We're not totally out of the woods as work will need to continue on the Glenorchy Road to finish the job, and the weather forecast for the coming week isn't looking great with snow affecting higher ground," the council said on Sunday.
It warned that the heavy rain, combined with milder temperatures and strong winds, was the perfect recipe for rockfalls which could could exacerbate current problems and create new ones.
"There remains a high risk of further rockfalls and slips across the district. Please continue to drive with caution and warn others, especially those who aren't so used to our winter conditions."
Heavy rain late on Saturday caused a slip on the zig-zags below Crown Terrace on the Arrowtown side of the Crown Range Road.
The road, linking Queenstown and Wanaka, remained open on a stop/go operation while the slip was cleared on Sunday. It was now fully open.
However, a rockfall warning was in place for the Crown Range and motorists should drive with caution.
Other potential rockfall areas were the the Lindis Pass (State Highway 8) and through the Kawarau Gorge and between Frankton and Kingston.
More heavy rain has been forecast for the Queenstown Lakes area, with snow possibly affecting the Crown Range.
The New Zealand Transport Agency said snow flurries were possible near the road's summit on Sunday afternoon but snow was not expected to settle.
Showers were forecast from early on Monday, falling as snow above 800 metres. Between 5am and 1pm on Monday, 5cm to 10cm of snow was expected to settle near the summit, with lesser amounts down to 800 metres.
