MetService is warning of heavy downpours and hail to strike in these northern regions, with intense rainfalls of up to 40mm an hour possible.
The forecaster said some storms could be slow-moving, causing flash flooding, especially in low-lying areas such as streams, rivers or narrow valleys.
It is also warning of slips and hazardous driving conditions with poor visibility in the heavy downpours.
In the meantime ominous dark clouds have turned Auckland to night, with flashes peppering overhead.
Drivers are being told to take care travelling on the rain-affected roads this afternoon and evening, and to exercise patience leaving the city.
NZTA said all motorways across Auckland were busy by 3pm and extra caution was advised as the wet weather settled in.
"Please remember to be patient and drive safely to your holiday destination this long weekend," said the transport agency.
