Fog was widespread across southeastern Australia on Friday morning, with visibility reduced to 100m or less in parts of NSW and Vic.

The combination of clear skies and relatively light winds over southeastern Australia on Thursday night allowed temperatures to cool enough for fog to form.

Image: Friday fog in Newcastle, NSW. Source: @babs_explores / Instagram

Friday’s first light revealed broad areas of fog and low cloud pooling in valleys across eastern NSW, the ACT and central and eastern Vic. The fog lasted for hours in some area before dispersing as the air warmed up.

Video: Visible true colour satellite images showing inland fog across parts of NSW, the ACT and Vic on Friday morning. The fog can be identified as stationary pools of white sitting in valleys, gradually disappearing as the morning progressed.

Friday morning’s fog reduced visibility to 50 metres at Richmond, Bathurst and Latrobe Valley, 100 metres at Camden and 200 metres in Canberra, Shepparton and Wangaratta.

Image: Fog at first light on Friday in Gundagai, NSW. Source: @margaretmoliver / Instagram

Fog is the term used when airborne water droplets reduce visibility at the surface to less than 1000 metres, while mist refers to visibility above 1000 metres.

Image: Fog and mist in Victoria's Macedon Ranges on Friday. Source: @sharonjyphotography / Instagram