Fog is a sure sign that winter is on the way and there was plenty of it across the country this morning. Clear skies and light winds allowed fog to form in a number of states and territories last night and this morning. Flights were delayed at Adelaide Airport where visibility was reduced to 100m at 7:30am today. The veil of fog also shrouded parts of the city and was particularly think in the nearby hills and Mount Lofty Ranges. Thick fog enveloped a number of places in New South Wales and the ACT this morning too. Visibility dropped down to just 50 metres in Campbelltown, Camden, Dubbo and Bathurst and between 100-200 metres at Glen Innes, Taree, Goulburn, Canberra and Newcastle. There was also noteworthy fog in Western Australia's Donnybrook, Oakey and Ipswich in Queensland and parts of northern Tasmania. You may have been wondering if you had fog or mist at your place this morning. It is called fog when visibility is below 1000m and mist when visibility remains above 1000 metres.