Environment Canada issued a fog advisory for the City of Toronto Wednesday afternoon.

“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 fog is expected to move further inland as the evening progresses,” the advisory says.

“Visibility may be significantly and suddenly reduced to near zero. Travel is expected to be hazardous due to reduced visibility in some locations.”

Commuting drivers are being told to slow down, watch for tail lights ahead and be prepared to stop if visibility is reduced.

Environment Canada issues fog advisories when near zero visibilities in fog are expected or occurring.

The Greater Toronto Airports Authority (GTAA), which operates Toronto Pearson airport, says 13 departing flights have been delayed so far due to the fog.

“To maintain safe operations, the flow of arrivals has been reduced by [NAV Canada] as a result of fog affecting the region,” the GTAA said.

“The airport continues to operate, but inbound flights may be delayed.”

Passengers are advised to check their flight status before leaving for the airport.