CityCat users faced 30-minute delays along all ferry services early on Friday, which was revised to five-minute delays just before 8am.

Planes arriving into Brisbane airport were delayed, with the foggy conditions expected to affect flights up to mid-morning.

Visibility was about 20 metres, according to the Bureau of Meteorology.

Motorists were urged to turn on their headlights and drive to suit the limited visibility.

The fog, which was spread across the south-east quarter of the state, was expected to clear to a sunny day, with a maximum temperature of 24 degrees forecast.