The MetService has issued a severe weather watch for much of the country overnight on Saturday and on Sunday.
It includes Northland, Auckland, Bay of Plenty, Rotorua, Nelson, Buller, Fiordland and Canterbury.
Heavy rain is forecast for the west of the South Island, also Northland, Auckland and Eastern Bay of Plenty, with northwest gales, with the possibility of severe gusts, for inland Canterbury.
The most rain is expected in Westland, with significant spill-over into the Canterbury headwaters, where heavy rain warnings remain in force.
For Northland and Auckland, a burst of heavy and possibly thundery rain is expected.
Local downpours may cause surface flooding.
For Eastern Bay of Plenty, heavy rain is possible.