Drivers should use caution when they get behind the wheel Thursday morning.
Environment Canada issued a fog advisory for Chatham-Kent, Windsor-Essex, London-Middlesex and Sarnia-Lambton, as well as all of Midwestern Ontario Wednesday evening.
The weather agency said dense fog patches are expected to develop late Wednesday evening and will last into Thursday morning.
Motorists are urged to use caution in areas of near-zero visibility. If visibility is reduced while driving, turn on your lights and maintain a safe following distance.