A special weather statement from Environment Canada says that the incoming system is developing in Colorado and will sweep into the province overnight.
The system is expected to hit the Windsor, Ont., area on Sunday evening, and reach large swath of southern Ontario stretching from Toronto to Georgian Bay by midnight.
Snowfall is expected to occur ahead of freezing rain in affected areas, until the temperatures rise to a point on Monday where the precipitation will become normal rain showers.
The Environment Canada website reports that southern Ontario is likely to see two to four centimetres of snow, followed by one or two millimetres of freezing rain.
Possible flight delays, cancellations
In Toronto, Porter Airlines was advising passengers that their flights could be cancelled or delayed as a result of the incoming weather.
The airline said its customers should check the status of their flights before heading to the airport on Monday.
Air Canada also advised passengers of possible flight problems because of the incoming freezing rain. People who planned to head to Pearson International Airport on Monday were asked to call ahead, or check their flight status online.