It said the winds "have the potential to cause damage" and made driving "difficult, especially for motorcycles and high-sided vehicles such as trucks and campervans".
Up to 300mm could fall about the Westland ranges and up to 250mm in parts of Fiordland, Canterbury and Otago, MetService said.
"This is a significant amount of rain for these areas and will cause rivers and streams on both sides of the main divide to rise quickly, make conditions on the West Coast roads and in the mountains very hazardous and could also cause slips," MetService said.