Portions of southwestern Ontario will get a winter belting throughout the rest of the workweek.
Environment Canada has upgraded the winter storm watch in Windsor-Essex and Chatham-Kent to a winter storm warning.
Forecasters say rain may start falling overnight, then become mixed with, then changing to snow Wednesday morning. The storm is expected to last through at least Thursday evening, with 20 to 30 centimetres of accumulation possible.
Snow may be accompanied at times by blowing snow, as wind gusts may reach 60 kilometres per hour, causing reduced visibility on roads.
"Surfaces such as highways, roads, walkways and parking lots may become difficult to navigate due to accumulating snow," read the warning from Environment Canada. "Visibility may be suddenly reduced at times in heavy snow. If visibility is reduced while driving, turn on your lights and maintain a safe following distance. Public Safety Canada encourages everyone to make an emergency plan and get an emergency kit with drinking water, food, medicine, a first-aid kit and a flashlight."
A winter storm watch remains in effect for London-Middlesex, Oxford, Elgin, and Norfolk Counties.
