A severe winter storm is gripping many parts of the United States. It's causing flight cancellations, blackouts and highway deaths, just as the Christmas holidays are beginning.

The storm is bringing blizzards and heavy snow to central and eastern parts of the country.

Weather authorities say about 200 million people, or 60 percent of the population, have been under weather advisories or warnings.

They are urging people to exercise caution against what they call life-threatening cold temperatures.

US media report more than 5,000 flights departing from or arriving at domestic airports were canceled on Friday alone, the highest daily number of cancelations this year. Reports say more than 1,000 flights are also set to be canceled on Saturday, hampering travel during the holiday season.

The storm also caused massive power outages in wide swaths of the country, including the southern state of Texas and the eastern states of Maine and New York. More than 1 million households are believed to have been affected.

Car accidents have been reported across the country, killing at least 11 people. They include a 50-vehicle pileup in the Midwestern state of Ohio that reportedly killed four people.

Some states have declared a state of emergency. New York state officials are urging people to refrain from traveling until around Sunday, as conditions are forecast to worsen through Christmas Day.

Heavy snow is affecting many parts of neighboring Canada, too. Local media are reporting a number of power outages in the provinces of Ontario and Quebec. They are also reporting cancelations of flights at major airports across the country.