A front is expected to move over the South Island on Friday preceded by northerly winds and heavy rain causing MetService to issue several rain warnings.
MetServuce says the front is likely to stall over Westland Friday night and may move southwards on Saturday, prolonging the duration of the rain.
Their forecasters expect between 200 and 300mm of rain over Westland and the Southern Alps from Friday evening through Saturday with lesser amounts spilling over into the headwaters of the Canterbury and Otago lakes and rivers.
They say further rain is possible on Sunday.
See all the latest rain warnings here.