Weather: Thunderstorm and heavy rain watch for top of North Island

Severe thunderstorms and flash flooding could be on the way for Auckland, Northland, Great Barrier Island, Coromandel, the Bay of Plenty and Rotorua, MetService says.

Forecasters issued a watch notice for the period from 6pm Sunday to midnight due to an unstable northwest airflow.

“…Whether these thunderstorms occur or not, there is a chance of localised downpours of 25 to 40mm per hour,” the agency said in a statement.

“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.”

They urged people to plan ahead, and be vigilant for changing or threatening conditions; and to stay updated on weather warnings.

“Driving conditions will also be hazardous, with surface flooding and poor visibility in heavy rain.”

The weather was expected to ease after 10pm for areas in the north.

Advice about how to prepare for a storm can be found here.