Dense fog patches across the Greater Toronto Area are resulting in near-zero visibility, Environment Canada says, and they could make for hazardous travel conditions during Monday's morning commute.

The federal weather agency has issued a fog advisory for much of southwestern Ontario, including York, Durham, Peel and Halton regions.

The fog set in overnight and isn't expected to dissipate until the morning.

Threat of freezing rain wanes

Meanwhile, freezing rain that was initially forecast to hit Toronto will likely miss most of the city, Environment Canada has clarified.

Other areas of southern Ontario and Quebec will not be so lucky.

A system known as a "Colorado low" will move across the lower Great Lakes on Monday, bringing with it "a significant freezing rain event," for the eastern reaches of southern Ontario and into Quebec. 

A special weather statement issued Monday morning, however, said temperatures will still hover around the freezing mark, meaning "some patchy freezing rain" is still possible in isolated pockets of the GTA.

Rainy day in Toronto

Most of the GTA will see some rain on Monday, while some isolated areas could have to contend with freezing rain. (David Donnelly/CBC)

The sloppy weather has forced the Peel District School Board to cancel buses in Caledon and Dufferin County. Similarly, both the Durham Catholic and Durham boards have cancelled buses in zones 1, 2 and 3. All schools remain open.

In Halton, both the public and Catholic boards have cancelled bus service on and north of Steeles Avenue, citing a "flash freeze.