MetService has issued a heavy rain and gale warning for most parts of the country for tonight and Monday.
It said the weather would hit the South Island today and tomorrow, before moving north.
The heaviest falls are expected in Westland.
MetService said rivers and streams would rise rapidly, and surface flooding and slips were likely, along with hazardous driving conditions.
Gale-force winds are likely tomorrow for Taranaki, the Marlborough Sounds and Wellington where wind gusts are expected to reach up to 130km/h.
On Sunday evening MetService said heavy rain had eased in Fiordland, Westland south of Lake Moeraki and the headwaters of the Otago lakes and rivers.