Hundreds of passengers flying in and out of Blenheim this morning have been left stranded as they wait for the fog to clear.
Two Air New Zealand flights from Blenheim to Wellington have been cancelled already this morning, with more delays expected.
A flight to Nelson scheduled to depart at 7am left more than an hour later. Sounds Air managing director Andrew Crawford said 200 passengers were booked to fly in and out of Marlborough today.
All Sounds Air flights were grounded until the fog cleared, Mr Crawford said.
No planes could land in Wellington or Marlborough, he said.
Passengers had been advised to wait until the fog dispersed or to reschedule flights.
The fog is forecast to clear mid-morning with temperatures in Blenheim expected to reach 30 degrees Celsius.
Travellers are advised to check with the airport's website or their airline for updates.
A whiteboard at Wellington Airport advised passengers there would be no flights until midday.
Air New Zealand advised Wellington passengers on cancelled domestic flights to return home and rebook.
The capital, which is today expected to have its hottest day of the summer, has been smothered in fog since 6pm yesterday.
While it was expected to disappear by mid morning, an Air New Zealand spokesperson said it had already caused headaches for more than 2500 people.
"Low lying sea fog is continuing to cause significant disruption to services into and out of Wellington this morning as well as flow on effects to other services on the Air New Zealand network."
The fog was created as warm, humid air clashed with the colder waters of Cook Strait.
- The Marlborough Express
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