Wild weather has lashed Auckland, prompting a warning to motorists and flooding at a shopping mall - with more thunder and strong winds on the way.

Auckland has copped a soaking this afternoon - with 50 lightning strikes reported and a deluge of heavy rain.

The MetService is warning Aucklanders to brace for a stormy night, with gale force northwest winds and thunderstorms set to hit Northland and Auckland between midnight and 6am Friday.

Motorists using Auckland's Harbour Bridge are warned to slow down due to strong wind gusts.

The National Institute of Water and Atmospheric Research said there had been 50 lightning strikes recorded in Auckland at lunchtime.

At least two stores at the Sylvia Park Shopping Centre in Mt Wellington have been closed to customers because of flooding issues.

Shoppers reported seeing water raining down inside the L'Occitane store.

Rachel Simpson told the Herald she walked past the boutique store as staff were positioning buckets to catch water leaking from the ceiling.

"I saw a few other patches [of leaks] near the store next door and you can see some rain water coming through the cracks.''

As weather condition worsen today, please remember to slow down, keep your lights on and maintain a safe following distance. Extra caution is also advised on the Auckland Harbour Bridge due to strong wind gusts. ^MF pic.twitter.com/qVYjVbMnQh

— NZTA Akld & Nthlnd (@NZTAAkl) August 22, 2019

Simpson said she walked past the area between 12.20-12.30pm and guessed staff had been working to keep things dry for about 20 minutes.

When she passed the store about 20 minutes later, a security guard was standing outside telling people not to take videos or photos.

By then one of the shops next door had been closed too, she said.

"The doors were closed but when I looked inside... there was water seeping through the door on the floor.''

Simpson, who lives just up the road from the Sylvia Park, said she regularly visited the mall.

In the past, during heavy rain and bad weather, she had seen staff bring out wheelie bins to catch water leaking through the ceiling.

NZ Fire and Emergency shift manager Scott Osmond said just after 1pm that they had not been called out to the mall for any flooding issues.

He said they had, however, been called to two or three "minor jobs'' where a tree had fallen down. But none of the call-outs had been very serious, he said.

Severe Thunderstorm Watch issued https://t.co/mCNwwqFyRt pic.twitter.com/oGlS8oF5OP

— Severe Weather Info (@MetServiceWARN) August 21, 2019

A spokesman for the shopping centre, Campbell Hodgetts, said: "There has been leaking in a couple of stores and we're just trying to get to the bottom of it.''

He said they had staff on the ground at the stores affected and he was due to be updated on the situation shortly.

The Auckland Emergency Management team is warning Aucklanders to be prepared for a windy, wet and thundery period - especially those on the west coast such as residents in Piha and Muriwai.

The authority warned people need to realise that overnight thunderstorms could reach severe status and there is a risk of localised damaging wind gusts and or a small tornado forming.

"It's a good time to secure outdoor furniture and make sure drains and gutters are clear. Remember to drive to the conditions.''

Satellite images Niwa shared on its social media platforms showed dramatic pictures of active lighting and weather activity over the upper North Island and wider Tasman area this morning.

So far in August there have only been three days with less than 1mm of rain reported at Auckland Airport. The weekend may bring another dry day to parts of the city, with a forecast of isolated showers.

Heavy rain and thunderstorms have blown into Auckland!

The Harbour Bridge faded from view 💨 ⛈️ pic.twitter.com/nOHpR4f78b

— NIWA Weather (@NiwaWeather) August 21, 2019

"Saturday is a more settled day for most Kiwis with a warming atmosphere and higher surface pressures across the country. However more unsettled weather is encroaching on the South Island during the latter half of the weekend," MetService meteorologist Angus Hines said.

The MetService has also got radar images showing active bands of showers bringing thunderstorms in and around the Auckland region at the moment.

People are being told to keep an eye on the forecast and to stay up-to-date in particular with any severe weather warnings, as there is a risk of severe thunderstorms overnight.

There are currently a number of severe thunderstorm watches in place - issued by the MetService - for Auckland, Great Barrier Island, the Coromandel Peninsula, Waikato and Waitomo.