What’s causing extreme cold in US Midwest

  1. A record-breaking cold wave has swept through the US Midwest and is stated to be caused by a polar vortex.
  2. The polar vortex is a large area of low pressure and cold air surrounding both of the Earth’s poles. The term “vortex” refers to the counter-clockwise flow of air that helps keep the colder air near the Poles.
  3. Polar vortex always exists near the poles, but weakens in summer and strengthens in winter. In winter, the north polar vortex sometimes becomes less stable and expands sending cold air southward with the jet stream. This is called a polar vortex event. Jet streams are a narrow belt of high altitude (above 12,000 m) westerly winds in the troposphere.