Much of the upper North Island is forecast to be hit by severe thunderstorms and possible surface flooding late on Tuesday.
MetService predicts that the thunderstorms could bring downpours of between 25 and 40mm per hour.
It said surface flooding and flash flooding were possible.
Severe thunderstorm watches are in place for Northland, Auckland, Great Barrier Island and western Waikato.
Northern Coromandel Peninsula, Waitomo and Taranaki have also been included.
A heavy rain watch has also been issued for the Bay of Plenty.
The thunderstorm watches are in place from 4pm until midnight, while Bay of Plenty's heavy rain watch is in place from 7pm until 6am Wednesday.
MetService said conditions should begin to ease in western areas from 9pm.
