Environment Canada issued a fog advisory early Sunday morning for Chatham-Kent, Sarnia-Lambton, London-Middlesex, Elgin, Oxford, Brant, Wellington, Huron, Perth, Grey, and Bruce Counties.
By 9:30 a.m., the advisory had ended for all of the regions as conditions improved.
The weather agency warned of areas of dense fog causing hazardous travel conditions.
When fog causes visibility to be reduced, motorists are warned to slow down, watch for tail lights, and be prepared to stop.