![Snow covered trees in Chicago amid the cold front that brought minus 25 degree temperatures. Meteorologists blamed a phenomenon called the polar vortex for the bitter cold that has descended on much of the central and eastern United States this week.(Photo/IC)](http://www.ecns.cn/hd/2019/02/02/1aec133dfc8848249f5aeb1467d7e4bc.jpg)
Snow covered trees in Chicago amid the cold front that brought minus 25 degree temperatures. Meteorologists blamed a phenomenon called the polar vortex for the bitter cold that has descended on much of the central and eastern United States this week.(Photo/IC)
![Snow covered trees in Chicago amid the cold front that brought minus 25 degree temperatures. Meteorologists blamed a phenomenon called the polar vortex for the bitter cold that has descended on much of the central and eastern United States this week.(Photo/IC)](http://www.ecns.cn/hd/2019/02/02/5acf3fec9c28423da209e19ef6fefcda.jpg)
Snow covered trees in Chicago amid the cold front that brought minus 25 degree temperatures. Meteorologists blamed a phenomenon called the polar vortex for the bitter cold that has descended on much of the central and eastern United States this week.(Photo/IC)
![Snow covered trees in Chicago amid the cold front that brought minus 25 degree temperatures. Meteorologists blamed a phenomenon called the polar vortex for the bitter cold that has descended on much of the central and eastern United States this week.(Photo/IC)](http://www.ecns.cn/hd/2019/02/02/494d9fae39ca44b3a646d25cfb888fcc.jpg)
Snow covered trees in Chicago amid the cold front that brought minus 25 degree temperatures. Meteorologists blamed a phenomenon called the polar vortex for the bitter cold that has descended on much of the central and eastern United States this week.(Photo/IC)