Several large patches of fog formed last night across New South Wales, Victoria and Queensland. A thick fog enveloped Richmond and Orange from around midnight, where soon after visibly plummeted to below 50 metres in some places. This blanket of cloud only dried out after 9am. The fog didn't make much further towards Sydney, although Bankstown still saw some patches last night and again in the morning around 7am. Further north in New South Wales, Lismore was also engulfed by a separate patch of fog overnight and into this morning where visibility fell to around 100 metres at 3am. Oakey in Queensland also experienced a thick blanket of low cloud, where visibility dropped to around 50m in the early hours of the morning. Patchier fog was also seen in the outer suburbs of Brisbane, including Archerfield and Amberley. Meanwhile, Wangarrata in Victoria also got some swathes of thick fog, with visibly at only 100 metres for nearly an hour. Residents are Kilmore would have also seen fog, but at much later in the morning. This fog, known as radiation fog, developed because skies were clear and winds were light across much of the east under a region of high pressure. As the earth's surface cooled overnight, it also cooled the air close to the ground. Temperatures dropped and humidity rose until water condensed, forming a shallow layer of surface cloud, or fog. Late tonight and early tomorrow morning, patches of fog could occur again around Bathurst as well as the areas around Albury, Young, Mudgee and Penrith. Victoria may get a few patches around Hunters Hill and in Wangaratta and surrounds.