MONTREAL -- Environment Canada is warning Montrealers and those in the surrounding regions to brace for smog in the morning and snow later tonight to begin a weekend of wet, winter weather.

EC issued a smog warning for Friday morning noting that there will be "high concentrations of fine particulates" that "will result in poor air quality" in the Montreal, Longueuil-Varennes, Laval and Chateauguay-La Prairie area.

Smog warning in effect in Montreal

The high concentrations of pollutants are expected to clear in the morning.

Health Quebec advises people to avoid exercise, particularly on busy streets, when there is a smog warning in effect, and to pay attention to physical symptoms when outdoors.

"If you have difficulty breathing, stay indoors," Health Quebec advises.

TWO DOZEN CENTIMETRES OF SNOW COMING

After clear skies for the remainder of Friday, about two centimetres of snow is forecast to start falling overnight, followed by heavy snow Saturday.

"Total snowfall amounts will reach 15 to 20 centimetres by Sunday morning," Environment Canada says.

The rapid accumulation of snow will make the roads dangerous, as visibility will be difficult. 

ACROSS QUEBEC

The Outaouais region will also see heavy snow with the forecast in the region predicting between 15 and 25 centimeters.

In the Laurentians, 25 to 30 centimetres will fall on Saint-Jérôme and Saint-Agathe, but no warning is in effect in Mont-Laurier, further north. Similar amounts of snow are forecast for Trois-Rivières and La Malbaie.

In Saguenay, Tadoussac, on the North Shore, in Bas-Saint-Laurent, in Gaspé and in the Matapedia Valley, the federal agency warns of 15 to 30 centimetres of snow. At La Tuque, snow accumulation should not exceed 20 centimetres.

In the regions of Drummondville, Sherbrooke, Thetford Mines, Lac-Mégantic and Saint-Georges, no snow warning was issued on Friday morning, though there will be precipitation which could be in the form of rain.

The regions of Abitibi-Témiscamingue, Chibougamau and the Lower North Shore should not receive significant amounts of snow on the weekend.

-- with reporting by the Canadian Press.