State Highway 94 was closed from East Gate (Hollyford) to The Chasm at 5pm today due to snow.
MetService said between 12cm and 18cm of snow was likely to accumulate about higher parts of the road in a 24-hour period from 9pm on Thursday, with lesser amounts down to 700 metres.
Milford Road Alliance earlier today said once cleared, the Southland highway would open at 9am but close at noon due to "significant rain and snow from late morning" as well as thunderstorms.
"The road will remain closed from midday Friday until mid-morning Saturday at this stage."
More snow and heavy rain was expected over the weekend.
The avalanche hazard is low.
Meanwhile, up to 3cm of snow was forecast for the Crown Range, linking Queenstown and Wānaka, from 2pm on Friday.
