A strong snow and ice storm followed by brutally cold conditions will soon smack the eastern two-thirds of the United States as frigid air escapes the Arctic, plunging as far south as Florida, meteorologists forecast.

Starting Saturday, millions of people are going to be hit by moderate to heavy snow from Kansas City to Washington — including a high chance of at least 8 inches of snow between central Kansas and Indiana — the National Weather Service warned Friday. Dangerous ice particularly lethal to power lines — “so heavy like paste, it’s hard to move,” said private meteorologist Ryan Maue — is likely to set in just south of that in southern Kansas, Missouri, Illinois, Indiana and much of Kentucky and West Virginia.

“It’s going to be a mess, a potential disaster,” Maue said. “This is something we haven’t seen in quite a while.”

National Weather Service meteorologist Alex Lamers said Friday that the potential for blizzard conditions is increasing, particularly in Kansas and neighboring portions of the Central Plains, and that wind gusts may reach 50 mph at times.

As the storm moves out on Monday, hundreds of millions of people in the eastern two-thirds of the nation will be plunged into dangerous bone-chilling air and wind chills all week, government and private forecasters said. Temperatures could be 12 to 25 degrees Fahrenheit (7 to 14 degrees Celsius) colder than normal as the dreaded polar vortex stretches down from the high Arctic bringing chilly weather, they said.

“This could lead to the coldest January for the U.S. since 2011,” AccuWeather Director of Forecast Operations Dan DePodwin said Friday. “It’s not just one day of this. It’s going to be three to five, in some cases a week or more of temperatures that are well below historical average.”

The biggest drop below normal is likely to be centered over the Ohio Valley, but significant unusual cold will extend southward all the way to the Gulf Coast, said Danny Barandiaran, a meteorologist at the National Weather Service’s Climate Prediction Center.

Forecasts have moderated a bit from last week when some computer models envisioned the worst cold spell in decades. Now it’s unlikely many cold records will break, but it will still have a big impact on the country, Barandiaran said.

There should even be a hard freeze in Florida, while areas near the Canadian border will be around zero, Barandiaran said.

“It’s not going to thaw out for awhile,” Maue said.

Woodwell Climate Research Institute climate scientist Jennifer Francis said the initial blasting winds from the north may shock people after a fairly warm last couple of years.