The winds had already ripped roofs from their houses and felled numerous trees throughout the region.
In Auckland, easterly gales were expected to strengthen with severe gales rising to 120 km/h are in exposed places.
Click here to view the current power outages.
The New Zealand Transport Agency has reduced the speed limit on Auckland Harbour Bridge from 80km/h to 70km/h and warned motorcyclists and drivers of high-sided vehicles to avoid the bridge altogether if possible.
Spokesman Ewart Barnsley said gusts of more than 60km/h had been recorded on the bridge today, with the wind forecast to get stronger overnight.
"We would urge people to travel only if they have to."
Motorists were advised to be aware of fallen trees and branches throughout the night.
Northland Police said heavy rain and strong winds have been battering the area and the weather was expected to worsen between 2am and 6am tomorrow morning.
Cape Reinga, a very exposed spot, has recorded a gust of 168km/h in the last hour! Purerua and Whangaparoa both gusting 85km/h ^RK
Northland road policing manager Inspector Murray Hodson said if possible, people should stay off the roads overnight.
"Watch out for surface flooding. If you hit a large pool of water it will be like skating across ice and you will have no control."
There had been reports of trees and power lines coming down and the roofs of 12 houses in the Kaitaia area were blown off in the high winds, Mr Hodson said.
A truck has crashed onto its side on State Highway 1 at Mangamuka and a tree has fallen onto a car on SH10 at Awanui, he said. The occupants were not injured.
Conditions worsening at RNZYS - Gusting 40 knots E. Stay off the water! @MetService @AklCouncil @AucklandCDEM pic.twitter.com/1q3KGp6mBw
Vector said strong winds and driving rain in Auckland had caused outages to about 9000 customers in the region. That number had been reduced to 7000 by 8.45pm.
The power cuts had been caused by trees and branches striking lines or bringing lines down, causing outages in Whenupai, Coatesville, Helensville, Takanini, Whangaripo, Waiwera, South Head, Muriwai, Tapora, the Kaipara hills and Kaukapakapa. There is also a larger outage in the Riverhead area.
"The predicted high winds, predominantly from the north east, have caused damage in the northern part of our network. It is predicted that winds will worsen overnight."
Vector crews and support staff were working into the night in an attempt to restore power.
Far North lines company Top Energy said almost 10,000 households in the region were without power at 5pm due to the severe storm. The number affected was expected to drop to 1100 overnight.
Properties remaining without power were expected to be reconnected by nightfall tomorrow, the company said in a statement.
Members of the public were reminded to stay clear of downed powerlines at all times.
Fuel for the heavy rain far northern areas. Loop on the link, photo attached: http://t.co/nTWWahqL8K pic.twitter.com/W9Hh8ZCanj
Up to 8000 Northpower customers are currently without power and more could be affected - bringing the total number without power in the region to 17,000.
Depending on the severity of the storm overnight, some customers could be without power for days.
However, network damage will be assessed tomorrow.
High winds have caused multiple outages in the Kaipara and Whangarei Districts since 5pm and more are expected.
About 3000 customers in rural areas around Dargaville township are without power and people are also affected in many other locations - Waipu, Maungakaramea, Poroti and Taipuha included.
WeatherWatch: (July 7) School holidays
Who to call:
* Vector electricity: North Shore, Waitakere or Rodney 0800 948 100 (option 1) Auckland, Manukau or Papakura call 0508 VECTOR (0508 832 867)
* Vector gas distribution (Auckland-wide): 0800 764 764
* Vector gas transmission (Auckland-wide): 0800 734 567
* Northpower (Kaipara and Whangarei districts): 0800 104 040
* Top Energy (Far North district): 0800 867 363.
