Since Thursday, large parts of the country have been paralyzed by the storm, which mixes snow, wind and freezing temperatures. At least 22 people died. Many roads are impassable and thousands of flights have been cancelled. Almost everywhere in American cities, such as Denver or Chicago, shelters have been opened to welcome people in need and give them the opportunity to warm up. The storm is expected to last through the weekend before temperatures return to seasonal norms by the middle of next week, the National Weather Service said.