The polar vortex is an area of cold air and low pressure which always surrounds both the North and South poles.
The meaning of the term vortex refers to the fact that the flow of air moves eastwards which helps keep cold air near the Poles.
Sometimes in the winter months, the northern hemisphere’s polar vortex expands and this consequently sends cold air southward through the jet stream into North America.
This has happened on a number of occasions including January 2014 and several colder outbreaks during the Winters of 1977, 1982, 1985 and 1989.
Other countries have also experienced cold surges connected to the polar vortex like parts of Europe and Asia.
The North and South polar vortex is a large scaled and persistent low pressure zone.
It rotates anti-clockwise at the North Pole (which is known as a cyclone) and clockwise at the South Pole, meaning that both the polar vortices rotate eastwards around each pole.
The base of the vortices are located in the middle and upper troposphere which also extend up into the stratosphere. Under that lies a large mass of cold and dense Arctic air.
A polar vortex will get stronger during the winter and weaker during the summer months, because it depends on the different temperatures between the equator and the poles.
These two vortices span less than 1,000 kilometres (620 miles) in diameter. Just like other cyclones the rotation of these vortices are driven by the Coriolis effect.
The first recording of a polar vortex dates back to 1853, in an issue of Littell’s Living Age, which was a weekly literary periodical which started in 1844.