A Severe Thunderstorm Watch is in place for Northland, with the stormy weather expected to stay until early tomorrow.
MetService says there is a moderate risk one or two thunderstorms could become severe, with possible localised downpours of 25 to 40mm per hour.
They say surface and flash flooding could be caused by this type of weather.
A Severe Weather Watch is in place for much of the upper and western North Island with heavy rain in store for Taranaki from 9am this morning, Northland from 12pm today, Auckland from 6pm today, and the Coromandel Peninsula and Waikato from 10pm today.
MetService said a humid northerly flow is brining the periods of possible heavy rain to the area.