Heavy rain could hit the country - starting in the South Island late tomorrow, brought by a low-pressure system

The West Coast, including Westland, Grey District, Buller and Nelson, will be the worst-affected - as well as Tasman and parts of Marlborough.

MetService Meteorologist Thapi Makgabutlane says most of the North Island can also expect falls on Friday.

She says central parts, Taranaki and the Tararua Range will all be affected.