TORONTO -- Much of southern Ontario is under a blanket of thick fog that has drastically reduced visibility on roads and highways across much of the region.

Environment Canada issued a fog advisory Saturday night that remained in effect Sunday morning.

The weather agency said it would likely be around noon before the mist lifts.

Some areas are also dealing with rain and drizzle as temperatures hover several degrees above the freezing mark.

Police are urging drivers to slow down and be extra cautious.

Air travellers, meantime, are advised to check on the status of their flights before heading to the airport because of possible delays and cancellations.