Residents in flood-prone areas of West Auckland are being asked to prepare to evacuate as bad weather causes power cuts and car crashes across Tāmaki Makaurau, with a severe thunderstorm watch in place for the north of the country.
Auckland Emergency Management said the severe weather across the city was worsening and it was trying to assess what action was needed.
If lives were at risk, residents should phone 111 immediately, it said in a social media post.
It also asked people to check on neighbours, friends and family members but not to put themselves in danger to do so.
Aucklanders have faced a chaotic commute ahead of the long weekend for the city's anniversary with some ferries cancelled, and crashes on the northwestern and southwestern motorways.
Police are urging Auckland motorists to drive to conditions by increasing following distances and being aware of fellow drivers and say people should delay any non-essential travel in the region.
The north, and north west, areas of Auckland have been particularly hit by the weather, police said in a statement.
There are slips on both Dome Valley Road and Kaipara Flats Road, forcing road closures and traffic diversions in those areas, they said.
Significant flooding is impacting several area across Tāmaki Makaurau, including parts of Taupaki, Albany, New Lynn, Henderson, and Kumeū, and police said drivers should take care when travelling through water-logged roads.
The public is advised not to travel to West Coast Beaches due to the sea conditions.
Police warned those travelling out of Auckland for the long weekend they may experience long traffic delays and potential diversions due to road closures.
Auckland Fire and Emergency said on Friday afternoon that every fire truck in Auckland was responding to emergency calls due to the bad weather and they had had to respond to more than 400 emergency calls today.
It said it was giving priority to people in danger and urges people to call 111 only if life or safety is at risk and the volume of calls was causing delays in answering them.
Fire and Emergency advised if water was entering your property, you should lift furniture and possessions without putting yourself at risk.
An amber alert was in place for the Harbour Bridge today from 7am until midday, meaning speeds were reduced and lanes could close.
Traffic on Auckland's motorways was heavy and slow on Friday afternoon.
Auckland ferries have been severely disrupted after a cruise ship lost its spring - the rope which attaches it to the wharf - this morning.
A Ports of Auckland spokesperson confirmed the ship had to use its engine to reattach itself.
The ship was the Noordam, which arrived in Auckland this morning and berthed at Princes Wharf.
The spokesperson said there were significant gusts of wind as the boat was reattached. It has meant ferries were held in Waitematā Harbour.
The website for Fullers Ferry lists several services - including from Devonport, Waiheke, Bayswater, Half Moon Bay and Birkenhead - as disrupted due to an incident with a cruise ship.
Ferries were already being disrupted by poor weather which has hit the region, causing the cancellation of some services this morning.
A severe thunderstorm watch has been issued for Auckland and Northland with bands of heavy rain and thunderstorms expected to move across Northland during the day and Auckland north of about Albany until early evening.
Some of these thunderstorms may produce downpours of 25 to 40 millimetres an hour, MetService said.
Orange heavy rain warnings are in place for Northland, Auckland, Coromandel Peninsula, Bay of Plenty west of Whakatāne and Mount Taranaki.
MetService said winds gusting 80km/h are also expected in Auckland over the coming days.
Vector's power outage map indicates cuts in Glen Eden, from West Coast Road extending south to Taiwini.
More than 1000 homes were also without power in Northland just before Friday midday.
By 10am Friday, Auckland Council had already had 30 requests for help and attended three flooding incidents.
The heavy rain has also meant black flag alerts have had to be issued at some Auckland beaches, due to wastewater overflows.
The "very high risk" warning is set to be in place until Sunday morning, when it drops to the red "high risk" alert.
There were 18 Auckland beaches deemed a very high risk for swimmers by Friday afternoon.
Northland and Coromandel
The subtropical low is bringing heavy rain to Northland and Coromandel as well as Auckland.
By mid-afternoon on Friday the Coromandel ranges had already been hit by up to 150mm of rain - the latest deluge of the area's sodden summer.
MetService figures show Coromandel was worst hit, but Kaikohe in Northland received a dumping of 100mm of rain by 2pm on Friday.
Auckland had received up to 80mm of rain in some places by Friday afternoon.
Part of State Highway 25A in Coromandel, which was already damaged by heavy rain earlier this month, has been closed between Kopu and Hikuai.
The road is one of the key roads for holidaymakers and locals travelling around Coromandel.
Waka Kotahi said the road between Kopu and Hikuai was closed until further notice due to "further road movement in wet conditions".
It is asking people to use alternative routes.
The state highway was beset with slips and cracks in the road surface.
At about 5.30pm on Friday, police advised that State Highway 1 at Brynderwyn was now closed to all traffic in both directions.
Thames Valley Civil Defence controller Garry Towler told Midday Report the arterial Tapu Coroglen and 309 roads - which link the west coast to the east coast - were also closed.
"On top of all of this, with all this rain which we're now getting to almost a metre so far this year, is that the Thames Coast Road and the road between Coromandel and Whitianga are now under traffic management due to slips that are starting to come down."
Crews had not had enough time to repair the roads in between the three storm events so far this year, he said.
"We're facing total saturation and the catchments just can't cope, and of course being a very hilly part of the country, we've just going these ongoing slips and issues with surface flooding."
High tide early on Friday afternoon could also be problematic for the region, he said.
Campgrounds have emptied out over the past day and Towler warned any travellers coming for the long weekend to check in before going.
"The catchments just can't cope" - Thames Valley Civil Defence controller Garry Towler
NIWA meteorologist Ben Noll told Morning Report it may not take much rain this weekend to see issues that arose during Cyclone Hale exacerbated in areas such as the Coromandel.
Noll said some places may see up to 100mm of rain.
"Through the day today we will see it spread south, into the Waikato, Taranaki and the Coromandel - and these are places that have already seen a lot of rain so far this January."
Saturday afternoon may bring a slight window of reprieve before the rain returns on Sunday, he said.
Festivals monitor conditions, Buskers Festival cancels Friday shows
A number of music festivals may also be called off.
The international buskers festival in Auckland has cancelled all shows for today due to bad weather.
Earlier, Buskers Festival managing directory Pam Glaser had said cancelling it would be heartbreaking as the performers had travelled from all over the world.
The show is due to go on for three days but although organisers decided it was unsafe to perform today, they are still hoping to stage the remaining shows.
Meanwhile, Elton John's Friday and Saturday night concerts at Mt Smart Stadium are set to go ahead, with organisers telling concert-goers to ensure they come prepared with a good raincoat or poncho as umbrellas will not be permitted for safety reasons.
Organisers of Monday's Laneway Festival say they are monitoring the conditions but expect it to go ahead.
The fate of Fat Boy Slim's concert on Sunday is unknown.
The Garden Music festival, Shakespeare in the Park, and the Folk festival are all still scheduled to go ahead.
Not all gloomy for Aotearoa
Christchurch is expected be the hottest place in the country this afternoon, with temperatures expected to hit 30 degrees.
MetService meteorologist Lewis Ferris said temperatures in Christchurch would peak between 2pm and 4pm.
After two very warm days in Christchurch, temperatures were expected drop substantially as a southerly front comes through about 7pm, Ferris said.
Most of the South Island is covered by total fire bans or restricted fire seasons due to the ongoing warm dry weather, with Otago's Alpine Zone the latest area to introduce a restricted fire season this morning.