Polar vortex causes Chicago River to 'smoke,' freeze as subzero temperatures hit foxnews.com

At the moment, temperatures in Chicago are lower than both Alaska and Antarctica. And signs of the bitter cold are all around — most notably surrounding the Chicago River, which is currently "smoking" and starting to freeze over while in the powerful polar vortex's grip.Aerial views of the Windy City reveal a large portion of the river is covered in chunks of ice and giving off swirling sea smoke, also known as "steam fog" when it occurs over freshwater lakes or rivers. However, it's important to note that fog technically occurs when warm air meets cold water.