Snow across Central and Eastern Canada caused headaches for travellers Tuesday with cancellations and delays reported at airports across the country.

Several flights leaving Toronto's Pearson International Airport were delayed Tuesday morning as a band of snow moved through southern Ontario and into Quebec.

As much as 20 centimetres was expected along the Highway 401 corridor from Sarnia to Kingston before the system moves into Montreal later in the day, where 15-20 centimetres was also expected.

Airports across the country — including Vancouver, Edmonton, Montreal, Ottawa and Halifax — showed delays and cancellations in their arrivals and departures throughout the day.

Travellers are being advised to call ahead before leaving home to catch their flights.

Shovels out in southern Ontario

The snow started early Tuesday in southern Ontario and was expected to move east into Newfoundland and Labrador by Wednesday.

Toronto received mixed snow and rain, with occasional heavy periods of snowfall north and east of the city, said Environment Canada.

Canada's largest city declared an extreme cold weather alert Tuesday, allowing officials to offer extra shelter space and services for the homeless. An alert usually comes into effect when Environment Canada predicts a temperature of –15 C or lower.

As the snow band moves out of the province later Tuesday, colder arctic air was forecast to move into southern and eastern Ontario overnight.

Many parts of Atlantic Canada, already shovelling out from a New Year's Eve wallop, will also see an extra 15-20 centimetres as the storm moves through late Tuesday and Wednesday.