A severe weather warning has been issued for Dunedin and North Otago as rain and strong winds brought by ex-cyclone Ita sweep down the country.
The wild weather has caused chaos in the upper North Island today, and MetService says the South Island will feel the sting later today and into Easter weekend.
Already, NZTA is advising of highway closures on the West Coast.
In Otago, rain is expected to pick up this evening and become heavy at times early tomorrow morning.
About 120mm to 180mm is expected about higher parts of North Otago from midnight tonight to midnight tomorrow, and 50mm to 90mm elsewhere, including Dunedin.
People are advised to watch out for rapidly rising streams and rivers, surface flooding, slips, and hazardous driving conditions.
Ugly weather is continuing to crash into the country today, but MetService says it is due to ease over the Easter weekend.
The atrocious conditions are being fuelled by ex-cyclone Ita, which is battering Northland and Auckland as it sweeps down the country.
Gale force winds and driving rain have caused road closures, power outages and slips around the country.
"Once the strong winds and heavy rain ease away, it will look far quieter and brighter. This should happen by Easter Sunday," MetService meteorologist Daniel Corbett said.
The intense band of rain and strong to severe gales will sink south to engulf central parts of the country by the end of today followed by slowly improving weather in the far north.
The rest of Easter weekend will bring a few passing troughs which could bring a bout of showers especially on the western coast, whereas eastern areas will stay mainly dry, Mr Corbett said.
Meanwhile, holidaymakers were being urged to take "extreme care" when travelling.
Winds gusted up to 98kp/h on the Auckland Harbour Bridge, there was surface flooding on sections of the city's motorway network, and debris littered rural state highways in both regions, New Zealand Transport Agency said.
The storm also caused damage, power outages and disrupted travel across Auckland city.
"We would encourage people going on holiday to do most of their driving during daylight hours when there's more visibility, particularly for those travelling on unfamiliar rural roads," NZTA national journey manager Kathryn Musgrave said.
"Although the worst of the storm has passed, there is still a risk of trees or branches loosened by the strong winds being a hazard for drivers - particularly at night."
By 2pm today, the fire service had responded to 770 emergency calls around the country related to weather.
Of those, 279 were in the Auckland region, 109 in Northland and 61 each in Waikato and Bay of Plenty.
At the storms peak, about 15,000 were without power.
Electricity company Vector said customers in Helensville, Greenhithe, Mangere, Titirangi, Orakei, Remuera, and Takanini had their power restored.
Customers remain without electricity in other localised areas, however crews were repairing damaged lines along with Treescape, clearing away branches, downed trees and other debris, the company said.
The wild weather has closed State Highway 25 from Hikuai in the south to Whitianga in the north.
Traffic was still using the Thames coast road, but there was some flooding around Goldfields Road in Nanaia, police said.
Motorists were encouraged to delay any travel plans to the peninsula until the roads were passable and open.
In Auckland, extensive flooding up to waist height in places forced the closure of Tamaki Drive, from the Strand to Kohimarama Road, from 9am today.
Auckland Council spokesman Glyn Walters said the city's Civil Defence and Emergency Management bunker had been activated as the council dealt with reports of surface flooding, downed trees, power cuts and debris.
Mr Walters warned there would also be localised surface flooding "all over then place".
At Devonport on the North Shore, a trimaran apparently broke free of its moorings and washed ashore. Photos show the yacht perched precariously on the footpath and foreshore of the beach.
Firefighters in the north of the country have been "flat tack" responding to wind damage this morning, with west Auckland and the North Shore apparently worst affected.
Northern fire communications operations manager Eric Smith said there had been a lot of calls to trees down on roads or power lines. There had also been calls to roofing tiles lifting.
In Wellington, strong winds gusting to 120km/h, and possibly 140km/h in exposed places, were expected today.
The wild weather has already brought damage to the capital, with slips blocking a road in Karori and forcing the evacuation of two buildings in Oriental Bay.
The first slip came down from the hillside behind an apartment building on Oriental Parade about 9.30pm yesterday. A water main also burst, and two buildings were evacuated.
A second slip blocked Nottingham St shortly before 6am today.
Further south, heavy rain was expected from about midday.
Holidaymakers are being urged to avoid all but essential travel to Coromandel as several key routes are closed due to flooding, slips and fallen trees, although some roads are reopening after foul weather forced their closure throughout the day.
Senior Sergeant Rupert Friend said the Thames Coast Road was open, allowing access to Coromandel Town and Whitianga.
State Highway 25 between Waihi and Whangamata was also open.
However, SH25A - Kopu Hikuai Road - was closed and would be for some hours yet, Mr Friend said.
SH25 south of Whitianga was also closed near to Wade Road, preventing travel between Tairua and Whitianga.
"Caution is urged on all coastal roads as the tide is coming in and high tide may well cause further road closures,'' he said.
Bay of Plenty motorists were also asked to disregard messages on electronic signs at Thames because they were incorrect and were unable to be changed due to a technical issue.
By 4pm today, the fire service had responded to 1071 emergency calls around the country related to weather.
