A sudden torrential downpour flooded about 70 homes in west and south Auckland in just three hours last night.
MetService said parts of Auckland received more than half their average rainfall for the month of July.
Seventy-seven millimetres of rain fell at the airport between 4pm and 9pm while other parts of the city received up to 30 millimetres in just one hour.
The fire service said the worst of the flooding was in and around Papakura, where the water rose about half a metre in some homes. Clendon and Manurewa were also affected.
It took 100 111 calls between 6pm and 9pm yesterday evening and visited about 70 properties affected by flooding.
It said cars were seen floating in one suburb, and several smaller roads were completely flooded.
Fire service spokesperson Jaron Phillips told Morning Report that the storm moved fast, starting in the west then moving south.
"We had reports of cars actually floating in one street in Papakura, and also Opaheke was quite seriously affected, with residents of some homes reporting up to knee-deep water levels."
Mr Phillips said firefighters pumped water out of many homes and managed to divert some water from reaching other houses, as well as clearing roads.
'Small river of water flowing down the hallway'
Glenys Ogg, who lives in south Auckland, said she first realised something was wrong was when her television went off. Her husband told her there was water inside the house but she initially thought it was a simple leak.
"I came up the stairs and there was literally a small river of water flowing down the hallway towards me," she said.
"It'd come through the garage, down into the main bedroom, two bathrooms, down the hall, downstairs to the kitchen, carried out down the hallway down to the lounge. It was quite a shock."
Papakura resident Emma Betts said intense rain about 7.30pm made her drain pipes overflow.
She said water then began to build up outside her garage, and the water level reached at least half a metre high.
Ms Betts said this was the fourth time this year such a thing has happened, due to poor drains outside her home on Elliot Street.
Lines company Vector said about 1600 homes in St Heliers lost power during the downpour, but it was restored within two hours.
It said most had power by 8.15pm, and the final 90-odd customers got their power back on about an hour and a half later.
Some roads around Auckland Airport experienced major flooding and were temporarily closed, but all are back open this morning and flights are running to schedule.