The worst of the heavy rain is expected to hit the West Coast today amid an ongoing "significant rain event".
The weather system is forecast to move north on Thursday, with parts of the North Island now in the firing line.
MetService has issued several weather warnings and watches right across the country. The warnings and watches cover most of the South Island, the lower North Island and Northland.
"This is a significant event for Westland, with potential for upgrade to a Red Warning," MetService said.
"People should listen to advice from local authorities, and those who need to travel through the region need to take extra care."
The forecasting agency added a significant amount of rain is expected in Southland and localised flooding is likely, especially in the west.
