Environment Canada has issued a fog advisory for a large swath of southern Ontario on Thursday.
The weather agency said the persistent fog will bring near-zero visibility in a widespread area.
It said it will continue throughout the early morning hours on Thursday but will dissipate rapidly throughout the middle part of the morning.
The fog advisory stretches from London through Toronto to Kingston and up towards Barrie and Peterborough.
“Travel is expected to be hazardous due to reduced visibility in some locations,” Environment Canada said.
“If visibility is reduced while driving, turn on your lights and maintain a safe following distance.”