A fog advisory is in effect for the city of Toronto and for Pickering, Oshawa and southern Durham Region.
Environment Canada issued the advisory at around 4:20 p.m. on Wednesday.
The agency said fog has moved in from Lake Ontario and is located “mainly along the lakeshore.”
“Particularly dense fog is situated between the lakeshore and the 401 in east Scarborough and Pickering,” the advisory read.
Environment Canada said the fog is expected to move further inland as the evening progresses.
The agency said visibility “may be significantly and suddenly reduced to near zero.”
“Travel is expected to be hazardous due to reduced visibility in some locations. If visibility is reduced while driving, slow down, watch for tail lights ahead and be prepared to stop,” the advisory warned.