Environment Canada has upgraded its winter storm watch to a warning for Sarnia-Lambton.
The national weather agency said the region can expect between 20 and 30 centimetres of snow by Thursday night.
Warning Preparedness Meteorologist Steven Flisfeder said rain is in the forecast on Tuesday evening, before transitioning to snow early Wednesday morning.
"That rain is starting Tuesday night and it's going to transition over to snow on Wednesday morning, likely around that 7 a.m. to 8 a.m. timeframe, so just in time for those morning commutes unfortunately. It's going to last through the day."
Winds gusting to 60 kilometres per hour are expected to cause reduced visibility in heavy and local blowing snow.
Flisfeder said it's tough to say whether or not there will be a break in snow throughout the day Wednesday.
"It could either stop completely or just taper off slightly depending on where you are exactly within the region," he said. "Most likely, areas closer to Lake Huron will see a bit of a pause rather than a less intense snowfall."
Environment Canada said snowfall rates could reach up to 2 cm per hour at times.
Motorists are urged to take their time and be careful on area roadways.