Thousands of flights have been canceled due to a snowstorm described by U.S. authorities as "once in a generation." Most areas of the United States have been experiencing a wave of cold and a severe drop in temperatures since Thursday.

The authorities also warned that travel conditions are extremely dangerous, at a time when Americans heavily use roads and airports during the holiday season.

According to the "FlightAware" flight tracking website, more than 2,350 flights were canceled in the United States on Thursday, and 2,120 more on Friday, while the Amtrak passenger railroad company canceled dozens of train trips during Christmas, disrupting the plans of tens of thousands traveling for the holidays.

Also, 8,450 other flights were delayed on Thursday, including more than a third of the flights operated by American Airlines, United Airlines, and Southwest Airlines.

The Federal Aviation Administration said on Thursday that the winter storm caused snowfall in the Midwest, with major travel disruptions expected in Chicago, Detroit, and Minneapolis-Saint Paul.

President Joe Biden issued an appeal to the public on Thursday saying: "Please take this storm seriously... I encourage everyone to listen to local warnings... the situation is serious."

Several states also declared a state of emergency, including Oklahoma and Kentucky, while temperatures will drop sharply reaching Texas in the southern part of the country.

According to U.S. authorities, snow and wind are likely to cause blizzards in certain areas, making any travel "dangerous and sometimes impossible."

Snowfall is expected to worsen by Friday and continue during the Christmas holiday weekend. The weather service in Buffalo, New York, went so far as to call it a "once in a generation storm."

The Midwest and Great Lakes region are expected to be particularly affected this weekend with blizzards.

Storms could reach speeds of up to 80 kilometers per hour, which could cause trees to fall and power outages.