Westland District Council has begun preparing for flooding, and is issuing sandbags to residents and businesses in the lowest lying streets.
MetService forecasts up to 750 milimetres of rain could fall in the next few days about the Westland ranges - especially between Otira and Fox Glaciers, and massive amounts of rain is expected across the entire Westland and Buller districts.
There are fears it could compound with high tides, thunderstorm downpours, and the water rushing off dry summer soils to create dangerous conditions and slips.
Westland mayor Bruce Smith says the rain began overnight, and high tide is expected just before 1pm on Wednesday.
He spoke to Corin Dann.
