Environment Canada has updated its special weather statement for Wednesday.
The weather agency says snowfall amounts of 10 to 15 cm are possible by Thursday morning.
Snow is expected to begin early Wednesday morning, before becoming heavy in the afternoon, then it will taper off to flurries by evening.
The storm from a Texas Low, will likely affect much of southern Ontario, as well as northeastern parts of the province.
Motorists are being reminded to adjust their driving to the conditions.