Spring officially arrived last weekend but another blast of winter weather is possible at midweek.
Environment Canada has issued a special weather statement for areas including Sarnia-Lambton, Chatham-Kent, Windsor-Essex and London-Middlesex.
After April-like temperatures and some showers Tuesday, a strong Colorado low will track towards southern Ontario.
Forecasters say freezing rain and ice pellets may be a significant issue to deal with across a large part of southwestern Ontario, later Wednesday and Thursday.
Significant snow is possible over areas extending from Lake Huron and Georgian Bay across northern parts of the Greater Toronto Area into eastern Ontario.
The national weather agency says the exact track of the low remains uncertain and even a slight northward or southward shift will affect how much snow, freezing precipitation or rain falls in any given location.
Motorists are advised, however, to be prepared for a return to hazardous winter driving conditions.
