Weather: snow falling on South Island highways - NZTA

Snow is falling on the South Island's state highways, the NZ Transport Agency says.

NZTA is advising drivers to be cautious on State Highway 8 between Omarama and Tarras, including the Lindis Pass, in Otago because of snow.

A wintry blast is heading towards the North Island, the MetService says, bringing below-average temperatures and frosty conditions later in the week.

Forecaster Gerard Bellam said a front was passing over the South Island on Saturday, with snow falling to 400m in Southland and Otago and 500m for the Canterbury region.

He said the frosty weather could extend as far north as the Coromandel and Auckland later next week.

A strong wind watch has been issued for Wellington, the Marlborough Sounds and the Kaikoura Coast, and a heavy rain watch is in place for the Wairoa District.

NZTA wanted drivers to plan ahead, with potentially hazardous snowfalls forecast. The worst falls were expected to affect major highways at Lewis Pass, Arthur's Pass, Porters Pass, Lindis Pass and the Crown Range Road.

NZTA said winter driving conditions could affect traction and urged drivers to slow down, increase their following distances, avoid sudden braking and to stay as visible as possible.

It also recommended carrying warm clothing, food and water in case of travel delays or detours.