Snow has already begun to fall on parts of Ontario and Quebec this weekend, with up to 20 centimetres of accumulation expected in what could be the unofficial start to the winter season.

Environment Canada has issued snowfall warnings across a large region extending from southwestern Ontario to southern Quebec, as a low pressure system from Texas heads north.

The snow arrived in many affected areas on Saturday evening. Affected regions could receive up to 20 centimetres of snow by Sunday morning.

Motorists are being urged to exercise caution, as they could face reduced visibility and other treacherous road conditions.

In Barrie, Ont., which is expected to receive 15 cm of snow, plows applied brine to some main roads – including the route for the city’s Santa Claus Parade – on Saturday morning.

In Perth County, northeast of London, Ont., emergency officials are warning drivers to stay off the roads unless it is urgent.

"When the roads get a little slippery there could be black ice," Perth County emergency management co-ordinator Dave Colvin told CTV Kitchener.

"We want you to stay safe, keep your family safe and other drivers on the road."

Meanwhile, city officials in Sudbury, which is expected to see 10 to 15 cm of accumulation, say they're ready to handle the year's first major snowfall.

The city plans to deploy its winter control plan, focusing on clearing and salting major roads, residential areas and sidewalks.

According to Environment Canada, the snow will taper off on Sunday afternoon in Ontario and Sunday evening in Quebec.

The following regions fall under the snowfall warning:

  • La Verendrye Wildlife Reserve
  • Temiscamingue
  • Abitibi
  • Greater Sudbury and vicinity
  • North Bay – West Nipissing
  • Manitoulin – Blind River – Killarney
  • Kirkland Lake – New Liskeard -- Temagami
  • Algonquin
  • Barrie – Orillia – Midland
  • Dufferin -- Innisfil
  • Grey – Bruce
  • Burk's Falls – Bayfield Inlet
  • Haliburton
  • Huron – Perth
  • Parry Sound – Muskoka
  • Waterloo -- Wellington

The first official day of winter is Dec. 21.

With files from CTV Barrie, CTV Kitchener and CTV Northern Ontario