Minimum temperatures have been on a bit of a see-saw during the last 48 hours, with the early morning mimum on Wednesday morning jumping by more than 10 degrees compared to early morning Tuesday, nearly eight degrees above the long-term monthly average for July.

The increased temperature was due to the insulating effect of extensive cloud cover overnight, associated with a cold front that swept over the southeastern parts of the country on Tuesday.

A high pressure system is clearing cloud across the ACT and NSW, meaning that Thursday's early morning temperature will likely again be well below freezing, and below average cold for this time of the year.

The recent front not only brought cloud with it, but rainfall associated with the system left some residual moisture over the southeastern parts of the country, likely just enough to bring about the formation of Canberra's favourite weather phenomenon.

Together with the clear overnight skies expected with the current high pressure system, this moisture brings an increased likelihood of fog across parts of the ACT on Thursday morning, including Canberra. Currently, forecasts are indicating that Canberra airport could be affected by fog and very low cloud from the early hours of Thursday morning, lasting well into the late morning.

For any road weather alerts issued for fog, visit https://www.weatherzone.com.au/warnings.jsp for updates.