Icy roads have been taking a deadly toll across Oklahoma and Missouri. At least 18 deaths are blamed on the storm, mostly from auto accidents.
Ice and winter storm warnings are up for parts of those two states as well as for sections of Kansas, Iowa and Illinois.
Oklahoma utilities say a half-million customers were blacked out as power lines snapped under the weight of ice and falling tree branches, the biggest power outage in state history.
And utilities in Missouri say more than 100,000 homes and businesses had no power.
Hundreds of flights in the Midwest have been canceled.
The storm has now spread into the Northeast as well.