Drivers are being warned of near-zero visibility on roads around the GTA today as a fog advisory remains in effect.

Environment Canada warned in an advisory early Thursday of “persistent fog with visibility near zero” in some areas.

The agency cautioned that “travel is expected to be hazardous due to reduced visibility in some locations.”

The advisory was in effect for the Greater Toronto Area and a wide swath of southern Ontario, but has since been reduced to Toronto and York Region

In a tweet, Ontario Provincial Police urged drivers to use their full headlighting system while the foggy conditions persist.

“I'm seeing a lot of vehicles, a lot of traffic, and a lot of people driving with just daytime running lights. That means no taillights, less visibility to the rear,” Ontario Provincial Police Sgt. Kerry Schmidt said in a video message on Twitter.

“Keep your full head lighting system on. Use your signals if you're changing lanes.”

Schmidt said that while some people put on their hazard lights when visibility is low, that is a “confusing factor” to other vehicles.  

“So unless you're suddenly braking, stopping or changing your driving behavior in a substantial way, do not use the four-way flashing lights,” he said.



Toronto Pearson International Airport warned that the foggy weather is causing some delays for arriving passengers.  

“To maintain safe operations, the flow of arrivals has been reduced by NAV Canada as a result of fog affecting the region,” the airport said in a tweet. “The airport continues to operate, but inbound flights may be delayed.”

Pearson is advising passengers to check their flight time and status with their airline before leaving for the airport.

Billy Bishop Airport also said the fog is impacting flights downtown.

“Fog and poor visibility may impact flight schedules this morning and lead to delays. Please check your airline for updates and current flight status,” the airport said.

When the fog clears, a mix of sun cloud is expected in Toronto for much of the day, with a high of 8C expected.

Periods of rain or drizzle are expected to begin after midnight with an overnight low of 5C.