Canberrans were not only greeted with frost on Sunday morning, but also saw sub-zero water droplets near the surface display a phenomenon known as freezing fog.  

As overnight skies remained clear over the eastern interior of the country, temperatures were allowed to plummet to below freezing. Locations across the tablelands, slopes and plains all recorded temperatures below freezing before dawn, while temperatures dropped to at least three degrees below freezing in Glen Innes, Mudgee, Goulburn and Canberra. Together with lingering moisture from recent rainfall, this created the perfect conditions for freezing fog to form over the ACT. 

Freezing fog is a phenomenon that occurs when very small water droplets suspended in the lowest levels of the atmosphere, that would normally form fog or mist, have temperatures somewhere in the range between 10 degrees below freezing and zero degrees. When temperatures at the surface are also at or below freezing, this allows for these 'supercooled' water droplets to freeze upon contact with any object or surface.

The phenomenon can cause serious problems for aviation services, not only by reducing horizontal and vertical visibility sufficiently to cause operational delays, but also requires the need for de-icing of aircraft preparing to depart from runways. 

An aviation weather warning for frost on the tarmac at Canberra Airport was issued overnight.