While the fog was spectacular for residents up above it in the hill suburbs, it caused issues for Air New Zealand ATR aircraft trying to land on the Taieri.
A Dunedin Airport spokeswoman said the affected flights were mainly to and from Christchurch.
Passengers made it to their intended destination, albeit a little late, after being placed on later flights.
MetService meteorologist Lewis Ferris said the thick fog was caused by a humid air mass which had been lingering over New Zealand during the weekend.
"It was pulled down from the north. What that does, being high humidity, it puts a lot of moisture in the air.
"So when you go into the night time, the air temperature drops down and that moisture condenses into fog. You only need to get a small amount of cooling for fog to form.""
He said fog covered the east coast of the South Island from Dunedin to Timaru for most of the morning.
Mr Ferris believed it was highly likely there would be fog again today.
"This is the time of the year [autumn, moving into winter] when fog will become more prevalent around the Dunedin region.""
