Auckland's already had waterspouts today and now it's under a severe thunderstorm watch.
Photo: Twitter / Brennan Mullan
The wider Auckland region and the Coromandel are subject to a warning from MetService about the conditions that could last until at least 6pm.
Severe thunderstorms can come with heavy rain - 25mm per hour or more, hailstones 20mm wide or larger and strong wind gusts up to 110 kilometres per hour.
Thunderstorms are already active in the region and hail has fallen in some Auckland suburbs.
Earlier in the afternoon, cumulus clouds - which are associated with heavy rain and thunderstorms - were seen building up over the city.
This morning, Waiheke Island residents saw at least four waterspouts form in the Hauraki Gulf.
Niwa meteorologist Ben Noll explained why the waterspouts occurred.
Waterspouts formed near Waiheke Island before moving into the Firth of Thames. Photo: Paul Dyson
"Right now our ocean temperatures around New Zealand and the Auckland region are about 20C, and this pocket of air above our heads is about 5C.
"That's a 15C temperature difference and that is enough to create instability in the atmosphere and therefore producing these tornadic waterspouts that we've seen around Auckland this morning.
"We also have relatively light winds ... that allows the waterspouts to basically not get ripped apart."