The South Auckland suburb of Takanini has been hammered in a sustained battering by hailstones "as big as marbles".
"It was intense and went on for quite a long time," said Andrea Larkins, an accountant at the Takanini Village.
She estimated the hailstones were 2cm in diameter and pelted down for 10 minutes.
She understood one shop at the shopping centre had water on the floor.
"Water built up at the entrance off Walters Rd. Hailstones blocked some of the drains as well."
Another woman who works at the shopping centre said: "There were some seriously large hailstones".
Pictures show water water pouring onto floors of shops and buckets placed to catch it.
The deluge came as part of a spring storm that led to lightning strikes in parts of Auckland.
Aucklanders are being warned to stay indoors if they hear thunder - and anyone on the water should get to land - after a series of forked lightning strikes across the city.
WeatherWatch reported late morning and afternoon that thunderstorms were popping up across Auckland after a relatively calm start to the day.
The lightning strikes forced Niwa to warn anyone on the water to come ashore immediately.
The MetService issued a severe thunderstorm warning for Warkworth, Puhoi, Kaipara Flats, Matakana and Ahuroa.
NewstalkZB's TimeSaver Traffic reported cars pulling over to the side of State Highway 1 from Warkworth to the Dome Valley as hail and torrential rain hit.
WeatherWatch warned the dramatic weather was not over yet.
"We expect more storms this afternoon."
As of 1pm the biggest area of concern was over South Auckland. Some flights were expected to be impacted.
Emergency services were called to the incident around 4pm.