Metservice has issued a thunderstorm watch for Northland, Auckland and Great Barrier Island on Tuesday evening.
The watch was issued at 5pm and is in force until 11pm.
"A front, with embedded thunderstorms is moving southwards over the upper North Island this afternoon and evening," Metservice said.
There is a moderate risk of severe thunderstorms with downpours of 25 to 40 mm/h for Northland east of about Kaikohe, and Auckland including Great Barrier Island.
Metservice says rainfall of this intensity can cause surface and/or flash flooding, especially about low-lying areas such as streams, rivers or narrow valleys, and may also lead to slips.
"Driving conditions will also be hazardous with surface flooding and poor visibility in heavy rain."
A heavy rain watch is also in force for Coromandel Peninsula until 4am, and Bay of Plenty from Opotiki westwards until 9am.
Metservice says periods of heavy rain, with thunderstorms and localised downpours, are possible in both regions.