Millions affected by freezing temperatures in the US

A dangerous cold snap has hit a large swath of the central United States, as a powerful storm moves eastward, causing disruption to travel and work from Kansas City to Washington DC.

Millions of Americans have been told to prepare for winter weather. West Virginia has joined five other states in declaring a state of emergency.

Kentucky, Virginia, Kansas, Arkansas and Missouri have declared states of emergency.

Forecasters say a strong pressure wave from the Earth's two poles has brought cold air from the Arctic to the central United States, causing severe weather.

More than 60 million people across the United States are under some type of weather alert, while air travel tracking network FlightAware shows nearly 2,200 flights canceled, with more than 25,000 others delayed.

High-speed winds from a storm system, the first of the year, have caused severe storms in Kansas and Missouri, while eastern states have been blanketed in several inches of snow.

Photos from Louisville's Muhammad Ali International Airport in Kentucky show planes covered in snow as the area is hit by a severe winter storm.

Kentucky Governor Andy Beshear urged residents to "stay home" after multiple car crashes caused major highway closures. The NWS also warned of the possibility of downed trees in many areas, as well as power outages.