The December 17–22, 2012 North American blizzard was a winter storm that affected the Midwestern and Eastern United States. Forming on December 17, the winter storm moved across the midwest, forcing schools to close throughout the region. Numerous warnings and advisories had been posted by the National Weather Service for many states, including Iowa, Nebraska, Illinois, and Wisconsin. Both O'Hare International Airport and Midway International Airport in Chicago, Illinois canceled most departures and arrivals. According to flight tracking website FlightStats.com, more than 1,000 flights were canceled across the region. More than 130,000 customers were without power across the west and midwest.