Severe storm warning in the north as wild weather continues

Auckland and the Coromandel will be hit by more nasty weather today.

MetService has issued a severe thunderstorm warning for Kaipara, Rodney and Whangarei and are warning residents to expect heavy rain and flash floods.

Large storms were detected moving in from the north-west towards areas including Helensville, Kaukapakapa, Parakai, Glorit, Shelly Beach, Maungaturoto, Kaiwaka, Brynderwyn, Paparoa, Taipuha and the Okahukura Peninsula.

A band of "torrential rain" is also heading in from the north-east, and weather analyst Philip Duncan said the two fronts were likely to merge over Auckland later this afternoon.

A severe storm watch is in place for Auckland, Northland and Great Barrier Island, with 430 lightning strikes detected in the last hour.

Forecaster John Crouch said rain would be heavy and persistent today with up to 30mm falling in an hour in Auckland.

"The heaviest falls are expected during this afternoon and evening, with thunderstorms. Between 50 and 100mm of rain may fall in some parts of Auckland today, including in the city," Mr Crouch said.

The Coromandel can expect thunderstorms later this afternoon and into the evening with up to 150mm of rain falling before 9am on Saturday.

"MetService forecasters advise the heavy rain will probably fall in a relatively short time, with some intense downpours leading to surface flooding, hazardous driving conditions, and possible slips. Stream and river levels could rise very quickly," Mr Crouch said.