Blame it on the “polar vortex.” That’s the weather phenomenon that has a huge mass of the North American continent shivering again this morning.

Extreme wind chills are forecast throughout all of Southern Ontario and beyond. It’s going to feel anywhere from minus-30 to minus-45.

Areas to the north of the GTA — in Barrie, Orillia, Midland, and Collingwood — are also under a blizzard warning.

It is so cold that skin can freeze in under five minutes if exposed to the wind.

Both the Toronto District and Toronto Catholic school boards have cancelled school buses today. Buses are also cancelled in Mississauga, Brampton, Caledon, York Region, Dufferin-Peel Catholic school buses, Wellington Dufferin, and Niagara. Schools are closed in Orangeville but open elsewhere for students who can get there.

Pearson airport has declared a “ground stop.” No planes are landing until 9:00 this morning because of a major backlog on the ground.

Some people have been sitting on the tarmac for four hours waiting for a gate to open up. It is so cold that ground personnel who normally service the planes and unload baggage can’t spend more than a few minutes outside at a time.

The TTC is also reporting that all of its streetcar lines will face delays today.