Summer is well and truly over and so the fog has decided to make its return over parts of Australia.The cooler nights and calm conditions are allowing areas of thick fog in the east.

In NSW, parts of the Illawarra including Moss Vale, Campbelltown and Bowral had low visibility this morning. Bowral and Moss Vale had visibility reduced to 50 metres or less.

In Victoria, Bairnsdale in Gippsland also received some fog, with visibility down to 150m.

Fog forms when air is saturated, winds are calm and temperatures are low. Fog in NSW and VIC is generally formed when warm moist air comes off the oceans in seabreezes, cools overnight (greater cooling under clear skies) and condenses early morning when ground temperatures are low.

The fog causes hazardous driving conditions especially when thick areas of fog appear and engulf drivers unexpectedly. It also poses a risk to pilots trying to take off or land.

Conditions are ideal for fog formation until Tuesday next week, with warm post summer sea surface temperatures, cool land temperatures at night, sea breezes and light winds.