The fog restrictions
set in just before 2am today.
Auckland's main domestic flight routes to Wellington, Christchurch, Dunedin and Queenstown had not been affected.
MetService reported the fog would clear in Auckland during the morning, but parts of Waikato would remain murky until this afternoon.
Passengers were advised to check Auckland Airport's website www.aucklandairport.co.nz or its app for the latest flight arrival and departure information.
WeatherWatch said the foggy conditions, across much of the upper North Island, were because of a centre of high pressure that crossed the country overnight.
The high pressure would bring with it light winds and a slightly more humid airflow.
A woman driving from west Auckland to the city on the Northwestern Motorway said she could barely see a metre in front of her car this morning.
"It looked like a ghost town. It was pretty dangerous. I really had to reduce my speed or risk a crash," she said.
Signs along the motorway warned motorists to take care.
Despite the fog in Auckland, it is now a relatively warm and fine day, with a high of 21C expected. Light winds were forecast for later today.
MetService forecasts that winds will pick up tomorrow, so the risk of a repeat of a disruptive foggy morning is reduced.
