Tens of millions of Americans are bracing for a major winter storm that could bring the heaviest snowfall and coldest temperatures in more than a decade.
The National Weather Service (NWS) said the storm, which originated in the central United States, will move eastward over the next two days.
A state of emergency has been declared in the states of Kentucky and Virginia. Areas accustomed to extreme cold, including the US states of Mississippi and Florida, have been warned to expect dangerous conditions.
Forecasters say the extreme weather is being caused by the polar vortex, an area of cold air that circulates around the Arctic.
“For some, this could be the heaviest snowfall in a decade,” the National Oceanic and Atmospheric Administration said.
AccuWeather forecaster Dan de Podon said: “This could be the coldest January for the US since January 2011.”
“Temperatures that are well below historical averages” could last for a week, he added.
Those low temperatures will also be on the East Coast, where the storm is expected to make landfall by Sunday evening.
In Central America, there will be “substantial disruptions to daily life” and “dangerous or impossible driving conditions and widespread outages” through Sunday, according to the NWS.
At least 8 inches (20.3 cm) of snow could fall in parts of Kansas and Indiana.
Blizzards are possible in parts of the Midwest.
The NWS warned that “whiteout conditions will make travel extremely hazardous, with impassable roads and an increased risk of stranded motorists”.
Heavy and freezing rain is forecast for parts of Missouri, Illinois and Kentucky and West Virginia.
As the storm moves east, millions more Americans will see record low temperatures, forecasters said.
Cities including Washington, D.C., Baltimore and Philadelphia are bracing for snowy and icy conditions Sunday through Monday. Parts of Virginia could see between 5 and 12 inches of snow.
Also on Sunday, parts of South America including Arkansas, Louisiana and Mississippi could see severe thunderstorms.
Private meteorologist Ryan Mao said: “It’s going to be a mess, a potential disaster. It’s something we haven’t seen in a long time.”
American, Delta, Southwest and United Airlines are waiving change fees for passengers due to potential flight disruptions.