Motorists are being asked to avoid all but essential travel in Waikato.
Roads are flooded throughout the region, especially on State Highway 1 through Huntly and Ngaruawahia.
Several cars have been damaged driving over potholes which have opened up in the downpour, on SH2 near the Pink Pig at Maramarua and north of Waihi.
Power company Vector says weather conditions are easing in Auckland, but crews are prepared for further power cuts due to potential thunderstorms on Saturday night.
A company spokesperson said there had been a few small power cuts in the city on Saturday because of felled trees.
Windblown debris also caused issues with the hot water network in the northern and western parts of Auckland, but most of these had been fixed.
Only minor problems in BOP and Coromandel
Civil Defence officials say there have only been minor problems from thunderstorms and heavy rain in the Coromandel and Bay of Plenty regions.
The same front which caused major flooding in Northland this week is passing over the area on Saturday night.
Civil Defence in Coromandel says the rain has now eased but flooding and slips have closed the Port Jackson road and Colville road.
It says the damage to the region is nowhere near as bad as the storm which devastated farmland at the tip of the peninsula last month.
In the Bay of Plenty, MetService is still warning there is a risk of flooding and slips from intense, localised downpours on Saturday night. But Civil Defence said it had caused no problems so far.
Police are advising people to avoid travelling until the weather clears.