A severe weather watch has been issued for heavy rain in the Coromandel Peninsula, and parts of Northland and Auckland including Great Barrier Island today.
MetService said a low pressure system and an associated front was slow-moving over the upper North Island today, bringing periods of heavy rain and isolated thunderstorms.
The wild weather is expected to weaken by the evening, but not before dumping heavy rain and thunderstorms in the afternoon.
Parts of the Coromandel Peninsula are already experiencing flooding today, with an orange heavy rain warning issued. The orange warning is a "take action" warning.
"Heavy rain may cause streams and rivers to rise rapidly," MetService warned in a statement. "Surface flooding and slips are also possible and driving conditions may be hazardous."
Between 60 and 90 millimetres of rain is expected to accumulate on top of what has already fallen in the area, especially in the north.
MetService advised people to keep up to date with forecasts.