At least nine deaths had been blamed on the weather.
Highway crews fought to keep up with slippery roads and in some places were blocked by fallen tree limbs and power lines. Ice had built up 3 inches thick in sections of Arkansas and Oklahoma.
The National Weather Service posted ice storm and winter storm warnings Tuesday along a broad swath from Texas and Oklahoma through the Mississippi and Ohio valleys all the way into northern New England. Radar showed smears of snow and freezing rain stretching from Texas to Virginia during the afternoon.
Broken tree limbs weighted down by ice crashed onto power lines, cutting service to at least 85,000 homes and businesses in hard-hit Arkansas, utilities said.
"I think we are about to go over the cliff," said Mel Coleman, CEO of the North Arkansas Electric Cooperative in Salem.
Arkansas utilities warned customers that their power could be out for at least three days.
"We fully expect this to be one of the largest outages we've ever had," said Coleman. "Right now, we're just hoping it's days and not weeks."
Kentucky state officials reported more than 40,000 customers with no electricity as ice up to 1.5 inches thick broke tree limbs.
"You hear the popping - it sounded like gunfire - and it's limbs from trees breaking," said Hopkins County, Ky., Judge-Executive Donald Carroll, who was among those with no power. He said crews in his western Kentucky county were busy trying to clear broken branches from roads.
"It's a serious situation," said Kentucky Transportation Secretary Joe Prather. "Our crews are working nonstop, but the snow in many areas is falling faster than we can clear, so it will take time to make headway."
About 6,000 customers were blacked out in Oklahoma as temperatures sat in the teens and 20s.
Kentucky Gov. Steve Beshear declared a statewide emergency Tuesday; Oklahoma Gov. Brad Henry did the same on Monday.
Meanwhile, in North Dakota, the National Guard was called out to remove snow in wind chill conditions that hit 40-below zero, reports CBS' The Early Show weather anchor Dave Price.
A winter storm warning has been issued for much of the Northeast overnight, reports Price. The big question for local authorities is whether they are facing a dusting of snow or the same deadly ice conditions that are blanketing much of the Midwest.
"It's pretty frightening," Guy Costa, Director of Public Works in Pittsburgh, told Price. "I was watching yesterday seeing what was going on in Kentucky and now we're going to be faced with that tonight."
Hundreds of public schools, colleges and universities called off classes Tuesday in parts of Arkansas, Oklahoma, Ohio, Indiana, Kentucky, Illinois and Maryland.
"Playing in the snow is pretty much the thing to do today," said student Sarah Bonham at Marshall University in Huntington, W.Va.
Every county reported school closings in West Virginia, where snow on hilly roads snow changed to sleet and to rain in places.
"The roads are still a little bit slimy," said Paul Howard, director of operations for West Virginia's Division of Homeland Security and Emergency Management. "The Division of Highways is knocking their socks off trying to keep the roads sort of clear."
Arkansas state government offices opened two hours late because of the weather, all but essential state workers in Oklahoma were told to stay home, and West Virginia state offices shut down early.
And as the storm threatened to barrel into New England, the New Hampshire Legislature canceled Wednesday's sessions. Up to 15 inches of snow was forecast Wednesday in New Hampshire.
Mammoth Cave National Park in south-central Kentucky was closed because broken tree limbs blocked roads, said Vickie Carson, the park's public information officer. "As soon as they get one area cleaned up, more trees fall," Carson said.
Since the storm began building on Monday, the weather had been blamed for three deaths in Arkansas, three in Oklahoma, two in Missouri and one in Texas.