A major storm system arriving in Montreal this morning is already causing problems at Trudeau airport.

The storm that claimed at least three lives, knocked out power to tens of thousands and cancelled hundreds of flights in the U-S Midwest blew into southern Ontario last night.

Toronto's Pearson Airport has cancelled or delayed about 20 per cent of its arrivals and departures this morning.

There are also a several flight cancellations at Trudeau Airport this morning and if you are meeting a flight you are advised to call ahead.

Environment Canada has issued a snowfall warning for Montreal.