In Buffalo (New York), it is storming and snowing.

DLNews Weather update:

Dead and injured - minus 49°F - power failures - mass crash - thousands of flights canceled

In Hendricks County (Indiana), it isn't easy to move forward by car.

It's freezing cold. And it storms. An arctic cold front with temperatures as low as minus 49°F plunged large parts of the USA into chaos shortly before Christmas. The reason: a "bomb cyclone."

A man tries to clear snow in Grand Rapids, Michigan, with a heating shovel on the barbie.

According to the U.S. Weather Service, 240 million U.S. citizens, or around 72 percent of the population of the United States, were affected by severe weather warnings. The number of dead rose to 17, as reported by the broadcaster NBC. At least three people died in a pile-up involving around 50 vehicles on the Ohio Turnpike.

But what is a "bomb cyclone"?

The storm has intensified into a "bomb cyclone," according to the website AccuWeather. It is caused by "bombogenesis," a phenomenon in which cold and warm air masses meet within 24 hours with falling air pressure. The weather service spoke of one of the most extensive weather warnings that had ever been issued. "We expect storms every winter, but this one is special," meteorologist Steve Flisfeder said. "A bomb cyclone is a strong low-pressure formation due to air mass contrasts in the United States. Frigid arctic air and warm subtropical air from the Gulf swirl into an extreme low. The cold wave with storms, ice, and snow in the USA and Canada will therefore continue until after Christmas." The chief meteorologist of the weather service in Glasgow (state of Montana), Rich Maliawco, warned of the dangers of such weather extremes. If people aren't adequately dressed in such temperatures, they "can get frostbite in less than five minutes," Maliawco said.

The Chicago skyline in a snowstorm.

Winter storm causes Christmas chaos.

Hundreds of vacationers are stranded at Miami Airport because of the weather.

More than 200 million people had received severe weather warnings. The north and central west of the country were particularly affected. But there were also warnings of extreme frost in states in the country's south. The U.S. Weather Service warned that "dangerous cold" is expected in the eastern two-thirds of the country over the holiday weekend. As a result, some states, including New York, have declared a state of emergency. Values of around minus 49 °F have already been measured in the states of Montana, South Dakota, and Wyoming. According to meteorologists, temperatures in Denver, Colorado, fell by around 40 degrees within 24 hours as the Arctic cold front passed through.

There were also chaotic scenes at the airports. Especially passengers in the north, around the great lakes, had to cancel trips. The airports in Chicago and Detroit are among the most critical hubs in the country.