Fog and low cloud is causing travel headaches in Queensland, New South Wales, the ACT, Victoria and South Australia. Visibility has dropped to just to a few hundred metres across a large area from Brisbane to southern NSW and the ACT to central Victoria to the Adelaide Hills, affecting many airports, including Sydney Airport. At Sydney Airport, fog is is uncommon given its proximity to ocean temperatures and wind. As in many cases the fog needed to be transported in light northwesterly winds from further inland where it typically forms. Visibility has become so low (as low as 200 metres) because of receiving more than 100 millimetres of rain in the past few days and now having skies clear. The clearing skies have allowed the air to cool and the moisture to condense into fog and low cloud. For much of southeastern Australia, this morning's fog should clear at about 9am, although could last a bit longer in the more prone sheltered areas. For Sydney Airport, some flights may not get going until about 8am when visibility is likely to have improved significantly with help from sunshine and extra wind. Good visibility should return by about 9am.