Auckland Civil Defence and Emergency Management was expecting more surface flooding and encouraged residents to avoid driving unless absolutely necessary.
Road closures were in place because of slips.
Oldfields, inland from Kaipara Harbour, had the biggest deluge with 100mm of rain falling since midnight Tuesday, followed by the satellite dish south of Warkworth with 92.5mm.
Adams said the typical rainfall for Whangaparaoa is 113mm and Whitianga is 187mm. Those towns have had 45mm and 77mm respectively, totalling around a third to half of their monthly average.
"It's fair thing to say a lot of places have seen half a month's worth of rainfall in one day."
Great Barrier Island was also exposed to the same heavy rain and possibility of flooding and slips.
The area of rain was narrow but intense, and there were thunderstorms in Northland.
Manager of Mangawhai Four Square Michael Patel said at its heaviest, the rain was like a monsoon. He saw thunder and lightning on Tuesday night but it had calmed down by the morning.
Metservice meteorologist Kyle Lee said the next few days would bring patchy showers as a front quickly moved across the country tomorrow and Saturday.
Sunday will be mainly fine.
Northern Fire Service shift manager Carren Larking said firefighters were called to save two people caught by rapidly rising floodwaters.
One stranded Wellsford resident could not get out of their Whangaripo Valley Rd property because of the height of the water.
Firefighters sandbagged the lower level of the inundated home and moved valuables to the second storey before the person was safely helped out of the waterlogged property.
A motorist called emergency services after being trapped by rising floodwaters on Waiteitei Rd, north of Wellsford.
When fire crews arrived they found three abandoned vehicles on the submerged road.
Deep flooding on State Highway 16 at West Coast Rd between Kaukapakapa and Wellsford had made the road impassable.
Auckland Civil Defence and Emergency Management is continuing to monitor the situation and is liaising with emergency services and MetService.
