Flooding in the Waikato township of Huntly is isolated to a few roads near the Waikato River, the fire service says.
There is flooding on Riverview Rd, Great South Rd, and on Mary St.
A slip hit a laundry, carport and car at one property on Riverview Rd, where the water is about 30cm deep and there were concerns cars would wash away.
An isolated downpour hit the area, and it was now a case of assisting residents and waiting for the water to recede, a fire service spokesman said.
He was not aware of any evacuations of people and said about half a dozen properties were affected.
Police say the local council is "attending a flooding event".
Riverview Rd is closed and diversions are in place.
Earlier rain and thunderstorms caused some surface flooding and power outages in Auckland.
The worst-hit Auckland area was East Coast Bays.
A slip at Waiwera also forced the closure of Waiwera Rd.
Weatherwatch.co.nz issued an alert for the Upper North Island on Sunday, predicting there would be localised flooding from slow moving, intense downpours.
Other North Island areas, including Bay of Plenty, Coromandel Peninsula, East Cape and Central Plateau also faced a drenching.
NZTA said there were several small slips on SH25 between Thames and Coromandel but all were passable.
The MetService earlier said a front moving eastwards across New Zealand on Sunday would bring rain to Northland, Auckland, Waikato, Waitomo, Coromandel Peninsula and Bay of Plenty.
Many of these regions were saturated during recent days, so surface flooding and slips were possible.