Frances Adank of Waka Kotahi NZ Transport Agency said the road was closed and it could take hours to clear.
A heavy snow watch was added to the raft of heavy rain and strong wind warnings this morning.
MetService issued the watch for Central Otago and Queenstown Lakes to run from 6am until 3pm tomorrow.
Heavy rain in the region is expected to turn to snow above 500 metres, with heavy snowfall possible above 700m.
Heavy rain warnings are in place for the headwaters of Otago lakes and rivers, Fiordland, Southland and Clutha.
Up to 300mm of rain is expected in the Southern Alps, with possible thunderstorms accompanying lower levels further east.
Southland and Clutha can expect 50 to 80mm of rain, especially northwest of Lumsden, until about 6pm today. Peak rates of 10 to 15 millimetres per hour are likely.
The rest of Otago, including Dunedin, is under a heavy rain watch for 24 hours from 11am today.
The heaviest rain is expected to fall this afternoon as a southerly kicks in and sends temperatures plummeting from 20C this morning to 10C by 6pm.
Balclutha (26.2C), Oban in Stewart Island(23.5C), Orari near Ashburton (28.2C) and Tautuku in the Catlins (25.6C) all hit their warmest September day on record yesterday.
It was Dunedin’s warmest September day in 14 years, reaching 24.7degC.
