State highways remain open across the South Island, but warnings are in place as snow, ice and freezing temperatures create difficult driving conditions.

The polar blast moved north on Saturday after heavy rain caused flooding on the West Coast on Friday.

NZTA said State Highway 94, the Milford Road, reopened on Saturday morning after an overnight closure due to the risk of snow.

More snow remained possible, while heavy machinery would be operating on the highway.

Warnings were in place for several routes, including State Highway 73 between Otira and Yaldhurst due to ice and grit.

Winter driving warnings also covered the Lindis Pass between Tarras and Omarama, State Highway 87 between Kyeburn and Outram, State Highway 85 between Kyeburn and Palmerston, and State Highway 1 between Palmerston and Dunedin.

Ice and grit were affecting State Highway 80 between Aoraki Mount Cook and Glentanner.

MetService had lifted most South Island weather warnings by 1pm.

A snowfall warning for Lewis Pass on State Highway 7 remained in place but was expected to expire later on Saturday afternoon.

NZTA urged road users to check weather forecasts and its Journey Planner before travelling.

Freezing temperatures and icy roads were expected across parts of the central and lower South Island over the next few days.