The first snow and ice is expected on South Island roads tonight

Temperatures will also drop in the North Island - hitting minus-four degrees in Taupo.

Road snowfall warnings apply across Canterbury's Lewis, Arthurs and Porters Passes - as well as the Crown Range road.

The Transport Agency's Tresca Forrester says although the snow may not settle - ice is a concern.

Motorists are advised to take extra care early tomorrow morning, particularly in shaded areas.