A weather watch for St. Catharines, Grimsby and the rest of North Niagara, has now been upgraded to a Winter Storm Warning.
Environment Canada says a major winter storm is expected tomorrow and Saturday, with travel becoming hazardous.
South Niagara is under a Blizzard Warning.
Rain overnight will change into snow tomorrow morning, winds will pick up to 90 km/h creating widespread blowing snow which will reduce visibility to near zero at times.
Snowfall amounts vary between 5 and 15 cm by Saturday morning.
It will become very cold, feeling like -20 tomorrow afternoon, freezing the rain that fell earlier in the day making for a possible flash freeze causing icy and slippery surfaces.
"Consider postponing non-essential travel until conditions improve. Visibility will be suddenly reduced to near zero at times in heavy snow and blowing snow. If visibility is reduced while driving, slow down, watch for tail lights ahead and be prepared to stop. 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."
The DSBN and Niagara Catholic Board have announced all schools will be closed tomorrow.