All flights to and from Hamilton airport tonight have been cancelled as thick fog continues to linger in parts of the Waikato and around Rotorua and Taupo.
WeatherWatch.co.nz said fog was lingering or had returned to parts of Waikato, generally from the Taupo/Rotorua area through to Hamilton and the Bombays.
While it was not widespread, the areas of fog were quite thick and were in more populated places or busier highways causing travel issues.
All four flights in and out of Hamilton tonight had been cancelled.
Motorists across Waikato and those entering the region from elsewhere should be prepared for sudden thick fog patches this evening.
The wind remained just offshore but northerlies were still expected to move in this evening and clear the fog away overnight or tomorrow morning. Tomorrow the winds would become blustery for a time later in the day.
Earlier in the day there was heavy fog in many parts of Auckland and Waikato and motorists were warned to drive to the conditions, as visibility was low.
Passengers due to board a flight from Hamilton to Christchurch early this afternoon were among those affected by delayed flights; having to be ferried to Auckland in buses to catch a flight from there instead.
A passenger told the Herald that just after 3pm there had been three busloads of people brought up to catch the flight in Auckland.
Air New Zealand spokeswoman Hannah Searle said low-visibility operations at Auckland Airport had been lifted just before 11.30am.
They were lifted at airports in Hamilton, Rotorua and Taupo at approximately 2pm.
Auckland Airport's Operations Centre said a total of 18 domestic regional flights had been cancelled due to the fog and 12 domestic regional flights had been delayed because of it.
No main trunk domestic or international flights had been affected.
It was not yet known how many people had been caught up in the delays and cancellations and whether any passengers had been travelling to Wellington for tomorrow night's big All Blacks and Lions test match.
Searle said Air New Zealand customers heading to Wellington who had been impacted by fog today were being reaccommodated on alternative services.