A huge area of fog formed on Thursday morning across parts of southeastern Australia which have been soaked by recent rainfall.

Fog is most common in Australia in late autumn, winter and early spring, and the first week of autumn is not normally a time you'd expect to a see such a widespread fog event.

But as you can see on the loop below from 7:30am to 11:30am (AEDT), a thick of blanket of fog was present in parts of South Australia, Victoria, the ACT and New South Wales before it burned off as the morning warmed up.

What caused the widespread fog event?

This event was caused by a combination of current weather conditions and recent rainfall.

In terms of today's weather, it was relatively clear and calm for much of the night, which allowed the air above the ground to cool sufficiently.

Extensive ground moisture from recent widespread heavy rainfall contributed to the air reaching 100% humidity (the saturation point required for fog to form) just above the ground.

Image: A distinct arc of morning fog through parts of Vic and SA which was gone well before midday on Thursday, March 5, 2026.

"This was very early in the season for such an extensive fog event," Weatherzone Director of Meteorology Duncan Tippins said.

"It was a product of the moisture content of the recently saturated soil from the recent rainfall event.

"Because we're only in early autumn, the soil is still warm which likely assisted the transfer of moisture back into the atmosphere."

As you'd expect after a foggy morning, many of the areas that were socked-in earlier are now experiencing sunny afternoons. For example, visibility was down below 50 metres at Mount Gambier Airport in South Australia around 5am today but local conditions have been clear since the fog lifted.