What you need to know in the wake of Auckland's storm:
Civil Defence is urging everyone in the Hobsonville area to stay indoors if they can.
MetService was warning conditions were ripe for further tornadoes and winds were still heavy in the area.
Warning signs of another tornado forming included a long, continuous roar or rumble, or a fast approaching cloud of debris which could be funnel shaped.
If another tornado hit, a basement offered the greatest safety, said Civil Defence.
Otherwise, people should remain in interior rooms or hallway without windows, on the lowest floor.
Avoid going to the top floors of homes or buildings. If another tornado struck it paid to get under something sturdy such as a heavy table or workbench and cover yourself with a mattress or blanket.
If outdoors try to avoid areas with any trees.
Civil Defence said tornadoes caused a lot of debris to be blown at extremely high speeds.
It was recommended that, if stuck outdoors, to lie flat in a low-lying area where the wind and debris would blow over.
"Protect your head with an object or with your arms."
If in a car, get out.
"Do not try to outrun a tornado in your car; instead, leave it immediately and do not get under your vehicle."
Civil Defence in the area is being run by Auckland Council.
Spokesman Glyn Walters said it was important people stayed up to date with the weather situation by listening to radio, watching TV or checking the internet.
"Check your roof for loose material that could blow around and be dangerous in strong winds.
"Pick up debris around your house that could become airborne," he said.
Boaties were being advised to check their moorings. and Walters said it went without saying, that people should take care driving.
MetService said more serious thunderstorms were highly likely, bringing with them more damaging winds and possible tornadoes.
"Very heavy rain can cause surface and/or flash flooding about streams, gullies and urban areas, and make driving conditions extremely hazardous.
"Very strong wind gusts can break branches from trees, damage roofing, and make driving hazardous especially for high-sided vehicles and motorcycles.
A severe thunderstorm watch remained in force for Auckland, Northland and Waikato.
The NZ Transport Agency has re-opened State Highway 18 (the Hobsonville Motorway) after it was closed when a series of tornados swept through north-west Auckland this afternoon.
The motorway was re-opened just after 4pm. It was closed in both directions just after 1.30pm. Storms brought down light poles, disabled motorway cameras and left sections of the motorway littered with debris.
SH18 was re-opened after NZTA contractors had inspected the motorway for damage and cleared debris.
"We had to be absolutely sure in the first place that it was safe for our contractors to be out making their checks, and then certain that it was safe for drivers to use the motorway again," NZTA's acting State Highways Manager for Auckland and Northland Steve Mutton said.
The motorway's Squadron Drive on and off ramps, however, remain closed until further notice.
The closure together with the storms is responsible for widespread congestion across the Auckland motorway network this evening.
"We're doing everything we can to get traffic running smoothly and safely, but journeys home tonight for some could be longer than usual. We ask drivers to be patient, not follow too closely and use their headlights in case heavy rain reduces visibility."
Mobile traffic in West Auckland was quite high, but Telecom said no major faults had been reported.
"There are obviously a lot of people making sure others are OK and figuring out where to go, but aside from a few minor issues there has been no affect to services there," a spokeswoman said.
A spokesman for Auckland Airport International said all scheduled domestic and international flights were now experiencing delays due to storm safety protocols being in place, which was restricting operations.
A number of arriving flights have been diverted to other airports.
Auckland Transport has tweeted that all train services are still running but there may be delays on the southern line as there is flooding at Pukekohe.
An emergency response centre had been set up at Whenuapai air base.
Twelve Urban Search and Rescue members were in the area gathering intelligence and had been sent out into the field.
The Defence Force was co-operating with the response and was standing by but had not yet deployed personnel.
St John spokesman Andy Gummer said:"So far seven people have been transported to North Shore Hospital with minor and moderate injuries.
"People were treated on the scene then transported."
The injuries occurred in a 1 km area.
* Take shelter, preferably indoors away from windows;
* Avoid sheltering under trees, if outside;
* Move cars under cover or away from trees;
* Secure any loose objects around your property;
* Check that drains and gutters are clear;
* Be ready to slow down or stop, if driving.
* Beware of fallen trees and power lines;
* Avoid streams and drains as you may be swept away in flash flooding.