Conditions appear primed for areas of fog to develop over parts of Sydney on Sunday morning. Winds will turn more onshore through the day today, directing slightly more humid air across the Sydney basin. Additionally, relatively warm and sunny conditions will provide the energy to cause some evaporation of water from any soil, vegetation and water bodies in the city. As winds fall light and the temperature drops under clear skies this evening and overnight, water vapour in the atmosphere will begin to condense into tiny water droplets. If enough water droplets form, the visibility will reduce below 1000 metres, and what we know as fog will form. Under these conditions, fog is most likely to form near lakes, rivers and grassy parks.