TORONTO (AP) — Schools were closed in Canada’s largest city of Toronto and commuters faced severe delays on Thursday as heavy snow continued to hammer much of southern Ontario, blocking streets and forcing cars into ditches.

Environment Canada said regions including the Greater Toronto Area, Kitchener and Hamilton are expected to see up to 30 centimeters (12 inches) of snow into Thursday afternoon.

Toronto, York, Peel and Halton Region schools closed Thursday morning, and institutions including the University of Toronto, Toronto Metropolitan University and York University announced their campuses were closed.

Complete school closures due to snow are rare in Toronto.

Environment Canada said the Ottawa area will see up to 25 centimeters (10 inches) of snow, tapering off Thursday evening. It added that northerly wind gusts of up to 60 kilometers (37 milies) per hour will result in blowing snow and reduced visibility, and a sharp temperature drop will cause very cold wind chills.

Provincial police advised residents to stay off the roads if possible, and officers responded to dozens of collisions and cars in ditches. Police said there were multiple road closures across southern Ontario, including ramps at the Highway 403 near the Burlington and Hamilton border and parts of Highway 401 in eastern Ontario.

Both Ontario Premier Doug Ford and Toronto Mayor Olivia Chow cancelled public events Thursday due to the inclement weather.

At Toronto’s Pearson airport, officials said air traffic management procedures were in place and impacting some arriving and departing flights.

Travellers were advised to check their flight status before heading to the airport, where snow clearing operations were underway.