Wild weather is continuing in parts of the country with heavy snow and strong wind warnings.

Snow is expected down to sea level in parts of the South Island today and tomorrow.

Heavy snow warnings are in place for Fiordland and parts of Southland, and snow is forecast for Dunedin, Clutha and Central Otago, Nelson west of Motueka, Buller and Westland north of Arthur's Pass.

Strong winds are forecast for Canterbury, Marlborough, the lower North Island and parts of Hawke's Bay.

Waka Kotahi NZTA senior journey manager Neil Walker said the Lewis Pass (SH7) was likely to stay closed until mid-morning.

All the passes were expected to have snow and the only question was how heavy, he said, and the motorway heading north from Dunedin was likely to be affected in the cold snap.

The message for anyone travelling in the South Island was to be vigilant and check weather and road conditions before they set out.

"Conditions can change at short notice so be really vigilant ... if you can avoid travel that's what we'd be recommending."

Auckland Harbour Bridge

Walker said the concern for the Auckland Harbour Bridge was wind speed, with the strongest gust overnight at 70 km/h.

Some lanes on the bridge would be closed if wind reached 80 km/h, and at 90 km/h they would look at closing the bridge, he said.

"Because we've got that temporary fix on there, if anything does occur on the day we're going to probably take a more cautious approach on closing the bridge."

A strut on the bridge was repaired last week after a truck, hit by a strong wind gust, crashed into it.

The agency advises avoid using the bridge if possible, travelling during off peak hours, using the western ring route or taking public transport.

Auckland Transport will look to replace double decker buses with single decker buses for services over the bridge today as a safety precaution, but Walker said there was plenty of seats on bus services.