The foul weather is thanks to a slow-moving front coming from the northwest and had already disrupted road travel on one state highway.
State Highway 35 is closed between Maraenui and Omaio, in eastern Bay of Plenty, due to multiple slips last night, Waka Kotahi NZ Transport Agency said.
Contractors were working hard to clear a number of slips, but it would remain closed overnight, with an update expected tomorrow morning.
"Heavy rainfall is expected to persist in the region into tomorrow, which poses additional risk. Conditions may be hazardous so please only drive if essential."
The detour route is via SH2 Waioeka Gorge.
Bay of Plenty and East Coast had experienced significant rainfall, coastal surges and strong winds this year, all of which put pressure on a roading network already more vulnerable due to unstable geology, the transport agency said.
"We understand it's challenging for people living and working along SH35 at the moment and we appreciate their resilience."
SH2 at Whirinaki in Hawke's Bay had reopened after being closed early this morning by a fallen tree between Whirinaki and Devil's Elbow, the agency said.
Meanwhile, police today warned motorists in the Rotorua area to drive to the conditions, with a slip on SH5 in Ngongotaha Valley, and surface flooding elsewhere.
Motorists should increase their following distances, put their headlights on and exercise patience so they reach their destinations safely, police said.
And the wet weather had also forced the biggest horse race meeting of the week to be called off, costing the racing industry hundreds of thousands of dollars.
The Hawke's Bay meeting in Hastings today was cancelled after heavy rain yesterday and overnight left the track too heavy and waterlogged for fair and safe racing.
The meeting, the second day of the three-day Hawke's Bay carnival, was to have contained the $300,000 Arrowfield Plate and the $140,000 Hawke's Bay Guineas.
Rain called off play for the second day in a row at the Carrus Tauranga Open.
Those who didn't finish their third rounds will head back tomorrow morning and push to complete their final rounds to see who will be crowned the latest Jennian Homes Charles Tour champion.
It was wet across most of the North Island today, with heavy falls in the north and east, but would ease for most tomorrow, MetService duty forecaster Sonja Farmer said.
"For the North Island over Sunday we've got rain and showers with heavy falls possible, easing for most but continuing in the Wairarapa, so we've still got that rain coming down the east coast of the island."
The lingering wet weather was thanks to a southbound low pressure system coming from the northwest that had been slowed by high pressure east of the North Island.
Aucklanders can expect showers, some heavy in the afternoon and evening - with possible thunderstorms - tomorrow, but it will be a mild 19C.
The extended forecast for Monday still brings possible showers for most of the North Island and rain in the south and east of the island, possibly heavy.
"Those heavy falls are moving away from the north of the island and hanging around the south and the east," Farmer said.
"So the north and the west probably getting a bit better on Monday."
South Islanders fare much better this weekend, with clear but cool conditions today continuing for most tomorrow.
Christchurch, Dunedin and Invercargill could expect settled weather and temperatures of 12C, 13C and 14C respectively.
