A blast of severe cold in the US Midwest forced the cancellation of more than 500 flights to be cancelled at Chicago's two main airports.
A weather pattern driving Arctic air south is keeping temperatures far below freezing. Chicago Public Schools called off classes for nearly 400,000 pupils.
In Michigan, roads closed as snow and freezing temperatures played a role in multiple crashes on Sunday. At least three people died over the weekend because of weather-related accidents.
Meanwhile the American Deep South is preparing itself for snow and ice.
Popular warm-weather tourist destinations including Charleston, Savannah, and New Orleans are expecting ice and even snow - both rare events in places that seldom see prolonged sub-freezing temperatures.
Delta Air Lines said more than 1,800 flights have been cancelled ahead of a winter storm.snow.
Forecasters were predicting snow and ice from Texas to the Carolinas by mid-week as precipitation moving in from the south met with cold air already chilling the region.