(CNN) The winter weather isn't done with Chicago; now there is talk of frost quakes. CNN affiliate WGN reported Wednesday that viewers in the Chicago area were awakened by a series of booms. On Wednesday, Amtrak canceled all service to and from Chicago -- a hub that typically operates 55 trains a day -- because of weather. According to the National Weather Service, the temperature in Iowa City at that time was about 21 below zero and it had been below zero all day. The National Weather Service projects that 75% of the US population will see below-freezing temperatures before Sunday.

Source: CNN January 31, 2019 09:56 UTC