Significant snowfall is in the forecast throughout the day on Friday, right across southwestern Ontario.
Environment Canada has upgraded a special weather statement to a winter weather travel advisory for much of the region, including London and Middlesex County, Sarnia-Lambton, Chatham-Kent, Windsor and Essex County, Oxford County, Elgin County, Huron County and Perth County.
The national weather agency said light snow is expected to begin Friday morning and intensify late in the afternoon or evening.
Environment Canada expects the system to drop 5 to 10 cm of snow, with higher amounts possible locally. There is also a risk of freezing rain for areas near Lake Erie Friday evening.
The evening commute may be significantly impacted by the snow.
"Motorists should expect hazardous winter driving conditions and adjust travel plans accordingly," Environment Canada said. "Be prepared to adjust your driving with changing road conditions. Slow down driving in slippery conditions. Watch for taillights ahead and maintain a safe following distance."
The snow will taper off from west to east late in the evening.