Thick fog shrouded parts of eastern NSW on Thursday morning, reducing visibility below 50 metres in parts of Sydney.

On Wednesday night, air near the ground over eastern NSW was loaded with moisture from recent rainfall. This airborne moisture allowed fog to easily develop as the temperature dropped during the night. By Thursday morning, the fog was thick and widespread, filling up valleys and flowing through the Sydney Basin.

Image: Fog over Sydney on Thursday moring. Source: @davey_rogers / Instagram

Fog initially developed about the ranges and western parts of Sydney during Wednesday night, before light westerly winds carried it towards the coast.

Visibility dropped below 50 metres at Camden Airport and close to 100 metres at Richmond Airport on Thursday morning.

Outside Sydney, visibility on Thursday morning was also reduced below 50 metres at Albury and to around 50 metres at Bathurst Airport and at Williamtown, near Newcastle.

Fog is a common occurrence over NSW during winter, particularly away from the coast and on cool nights after rain has fallen.