Thunderstorms are brewing in the Tasman and set to hit the West Coast of the North Island from midnight tonight, with hail, strong winds and possibly tornados in coastal Waikato and Taranaki.
A severe weather forecaster with MetService John Crouch said any tornados were likely to be quite small.
But Mr Crouch said along with the high winds, they could damage trees and powerlines and make driving dangerous.
He said the thunderstorms would move across the North Island during the morning and should be over Coromandel and Bay of Plenty by early afternoon.
MetService also said a complex trough was expected to bring bursts of heavy rain to the upper South Island and lower North Island tomorrow morning.