The Arctic is much warmer now than it was 30 years ago. They even had 100° days in Siberia last summer. The warming Arctic has caused changes in the jet stream, which controls the Northern Hemispheres’ weather. The Rossby waves in the jet stream,  that move from west to east across the United States, (see picture), now come down further and move slower from west to east.

This means that the jet stream can sometimes pull Arctic air down from the Arctic region, called a Polar Vortex. The slower movement of the Rossby Waves causes the extreme cold to persist for longer. It is 3° today in Kansas, the windchill is -15°, and this cold spell will persist for about a week. If it is extremely cold and snowy where you live, you can thank global warming for that.