There are flight delays and cancellations at Auckland Airport and delays on roads and in ferry services as fog blankets the area.
As at 10am at least 15 domestic flights had been cancelled and 10 delayed.
The airport said two main trunk domestic flights had also been cancelled and four delayed.
International flights are not affected.
Motorists have also been warned of the fog by NZ Transport Agency Waka Kotahi.
"Please take extra care on the roads this morning with reduced visibility due to fog affecting much of Auckland. Remember to keep your lights on, allow extra time and mind your following distance."
Auckland Transport said delays to all ferry services "due to extreme fog in the harbour" should be expected.
