Tens of millions of Americans are bracing for a massive 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 started in the central United States, will move eastward over the next few days.

Kentucky and Virginia have declared states of emergency Warnings have been issued for parts of the country not accustomed to severe cold weather, such as Mississippi and Florida, where dangerous weather is expected.

Forecasters said the extreme weather was caused by the polar vortex, an area of ​​cold air that circulates around the Arctic.

“For some, this could be the largest snowfall in more than a decade,” the National Oceanic and Atmospheric Administration said.

“This could lead to the coldest January in the United States since 2011,” AccuWeather forecaster Dan DePodwin said.

He added that “temperatures well below historical averages” were likely to persist for a week.

Cold temperatures will also be felt along the East Coast, where the storm is expected to arrive Sunday night.

In the central United States, there will be “significant disruptions to daily life” and “hazardous or impossible driving conditions and widespread closures” through Sunday, according to the National Weather Service.

Parts of Kansas and Indiana could see at least 8 inches (20.3 centimeters) of snow.

Blizzard conditions are possible in parts of the Midwest.

“Heavy snow will make travel extremely dangerous, with roads impassable and a high risk of stranding motorists,” the National Weather Service warned.

Sleet and freezing rain are expected across large areas of Missouri, Illinois, Kentucky and West Virginia.

Forecasters say millions of Americans will be hit by record low temperatures as the storm moves east.

Cities such as Washington, D.C., Baltimore and Philadelphia are bracing for snow and icy weather Sunday into Monday. Parts of Virginia could see 5 to 12 inches of snow.

Also on Sunday, severe thunderstorms are possible in parts of the southern United States, including Arkansas, Louisiana and Mississippi.

“It’s going to be chaos, a potential disaster. It’s something we haven’t seen in a long time,” said private meteorologist Ryan Maue.

American Airlines, Delta Air Lines, Southwest Airlines and United Airlines are waiving change fees for passengers due to potential flight disruptions.