Environment Canada says up to 15 centimetres of snow is expected to hit Waterloo Region, Guelph and Wellington County on Wednesday.
The agency says snow will become heavy during the afternoon and continue through the evening before tapering off during the overnight.
Strong snow squalls with heavy, blowing snow are expected to follow on Thursday afternoon and continue into Friday, Environment Canada said.
As of Wednesday morning, a snowfall warning had been issued for Guelph and Wellington County, while Waterloo Region remains under a special weather statement.
A snow squall watch was also issued for Guelph and Wellington County on Wednesday afternoon.
Environment Canada is warning commuters to be ready for poor winter driving conditions due to low visibility in heavy snow and quickly-accumulating snow.
The cities of Kitchener, Waterloo and Cambridge each declared a snow event, meaning residents had to get their car off the street by midnight or risk being ticketed or towed.