Severe weather watches are in place for some parts of top of the South Island and east of the North Island.
Heavy rain watches are in place for the eastern Bay of Plenty and Tasman, west of Motueka until Wednesday evening.
MetService said rain was expected for most of the North Island and top of the South on Wednesday.
Northland to Taranaki may experience possible thunderstorms along with heavy rain in the morning.
Heavy rain could also be expected overnight in the north of Buller, Nelson and Marlborough regions.