Snow forecast over the next few days means the Milford Road will close overnight between the Hollyford Road Junction and the Chasm from today.
Snow on the Milford Road this morning. Photo: Supplied
Waka Kotahi said travel to and from Piopiotahi Milford Sound could not be guaranteed this weekend.
Heavy snow was forecast throughout the day on Friday and it was unlikely the road would fully reopen.
A convoy in and out was planned when lighter snow was forecast between 10am and 12 noon on Friday but that depended on snow clearing progress.
Convoy times would be confirmed on Friday morning.
Further snow was forecast over the weekend but was set to clear over the weekend.
Warning over weekend weather
Motorists should expect winter driving conditions heading into the weekend with snow forecast for Otago, Southland and the main divide through Canterbury.
Waka Kotahi journey manager Tresca Forrester said people should prepare for cold and wintery conditions across the southern and central South Island and the lower North Island.
Alpine passes will be affected by snow and restrictions or closures could disrupt travel.
Forrester said people needed to drive to the conditions and be prepared for the weather.
Waka Kotahi highway patrols would be out ahead of the bad weather, grit runs are prepared for snow clearing and will continue through the day and weekend as required.
Road crews use a combination of calcium magnesium acetate and grit to control ice on the roads.
"Road users need to drive at much slower speeds in these conditions, gritted or not," Forrester said.
"Allow for much greater braking distances and avoid braking suddenly."
People travelling across regions from this weekend are advised to pack warm clothes, food and keep up to date with weather forecasts and the latest roading conditions.
Motorists should be prepared for road restrictions, road closures and long delays.
Carrying chains and knowing how to fit them may be required when travelling on some South Island roads, including Arthur's and Porters Passes (SH73), Haast Pass (SH6) Burkes and Lindis Pass (SH8), Milford Road (SH94) and State Highway 75 between Akaroa and Christchurch.
Another weather front on Friday is forecast to bring heavy rain and strong winds, with possible squally thunderstorms in western areas.