Thunderstorms, which have already caused surface flooding, ripped yachts from their moorings, felled trees and resulted in a plane being stuck by lightning, are expected to continue pounding the north of the country tonight.
More than 1000 homes in the Auckland suburbs of Westmere and Point Chevalier were without power for about an hour this afternoon due to the stormy weather, while Fullers had to cancel its ferry service between Waiheke Island and Birkenhead due to rough seas.
MetService has issued a severe weather warning for Bay of Plenty, where up to 26mm of rain has been recorded.
Parts of Northland had 36mm and Auckland 20mm.
WeatherWatch.co.nz head weather analyst Philip Duncan said conditions for much of the north would clear by morning but the rain would be back for some areas on Friday.
Unusually warm temperatures for May, with humidity at close to 100 per cent, were causing lightning in some areas and this was expected to continue overnight, he said.
WeatherWatch.co.nz had received reports of yachts breaking free of their moorings in Opua in the Bay of Islands and of surface flooding in Dargaville.
A Qantas Boeing 737 jet bound for Melbourne with 144 passengers was forced to return to Auckland this afternoon after the pilot suspected the aircraft was hit by lightning.
The aircraft was taken out of service for examination and the passengers transferred to another flight.
The Fire Service had attended 12 weather-related incidents, including felled trees and leaking roofs, up to 6pm.