A severe cold snap has struck the Midwest of the United States and is expected to spread to the Northeast, which has already seen several days of heavy snowfall. The unusual weather conditions, known as a "polar vortex," could send local temperatures to their lowest points in 20 years. Authorities in many places have urged residents to stay indoors and stock up on food, while the National Weather Service described the cold as "life-threatening." More than 1,300 flights were canceled on January 5 at Chicago's O'Hare Airport, one of the country's busiest airports.
