Big thunderstorms hit parts of the North Island this afternoon, with downpours and hail reported.
The forecaster said the Coromandel Peninsula near Thames was being bit by a "major'' thunderstorm this afternoon.
South Auckland, and the area from Howick to the Hunua Ranges were expected to bear the brunt of thunderstorms this afternoon, with possible flash flooding and lightning strikes in some areas, according to WeatherWatch.
Thunderstorms formed across the southeast and south of Auckland.
WetherWatch warned a patchy line of showers and large clouds could bring downpours which were heavy enough to to cause localised flash flooding and lightning strikes.
"Hail is also possible along with funnel clouds. Heavy showers and isolated thunderstorms will continue to bubble up this afternoon around Auckland and much of the upper North Island. However, around these showers it should remain mostly sunny, hot and dry,'' WeatherWatch said.
WeatherWatch said most of the North Island had a risk of significant thunderstorms which could lead to localised surface and flash flooding, hail and even funnel clouds.
Head weather analyst Philip Duncan said tropical-like afternoon heat showers could form rapidly.
"If you're watching the clouds today you'll be able to see where the biggest cloud build-ups occur. The one's that look a bit ominous probably are.
"If a thunderstorm forms near you then the best place to be is indoors - and remain there until the thunderstorm passes.''