This is the dramatic moment thick fog engulfs Sydney Harbour, obscuring the iconic Opera House in Australia.

Footage shows dense haze blanketing the city, with high-rise buildings barely visible in the background on Tuesday, August 5, around 7 am.

Moments later, the fog began to lift, revealing the Harbour Bridge and one of the world's most famous landmarks.

Dozens of flights and ferry services were cancelled in Sydney as the unusual weather event caused significant delays for commuters.

The fog was expected to clear by late morning, with Sydney forecast to reach a high of 21 degrees Celsius.

Fog develops when warm, moist air cools and water vapour condenses into tiny droplets suspended in the air. This typically occurs when temperatures fall to the dew point, often overnight or early morning, creating a thick mist that reduces visibility.