MetService have issued a 'Red' heavy rain warning for the West Coast and an 'Orange' for Fiordland

The warnings are in effect from early Wednesday morning, with up to 130mm of rain expected for Fiordland .

Further north on the West Coast up to 500mm could fall from 1am Wednesday to Thursday evening, as well as thunderstorms.

MetService say heavy rain may cause streams and rivers to rise rapidly.

Surface flooding and slips are also possible and driving conditions may be hazardous.

Waka Kotahi NZ Transport Agency (NZTA) are urging drivers and residents to be ready for extremely heavy rain from the early hours of Wednesday.

NZTA Journey Manager Tresca Forrester says people need to assess how urgent their trip is before heading out on the West Coast over Wednesday and Thursday.

“Roads will be affected and driving will be treacherous in such heavy downpours. People may face delays.”

A similar storm system caused significant flooding and high river levels in Buller and Marlborough mid last year.