Motorists beware... one of the worst storms of the decade is set to wreak havoc this weekend

Severe weather warnings and watches issued by the MetService cover almost all of New Zealand.

In Auckland, sandbags are weighing down the temporary road cones along the Harbour Bridge.

Tow trucks are also on standby on either side of the bridge to respond quickly to crashes and breakdowns.

A heavy snow watch is in place in Clutha, Central Otago south of Alexandra, Southland, Fiordland and Stewart Island.

AA Spokesperson Barney Irvine warns people should keep an eye on the news.

He advises people not to drive if the weather is very bad -- and if they must -- to drive to the conditions.