1. National

US temperatures set to plummet to record lows

Parts of America and Canada are experiencing near record-breaking low temperatures from a severe winter storm that has claimed at least 16 lives.

View all 43 updates ›

What is a polar vortex?

The polar vortex, or polar pig, as it has been dubbed by some media commentators, is:

  • A large dense area of cold air formed in a polar winter
  • Normally found rotating hurricane-like around the North or South Pole
  • A low pressure area with winds that can exceed 100mph
  • Around -80 degrees Celsius
  • Strong enough to sustain its own low pressure, sealing in cold air like a fridge
  • Tens of thousands of feet above the atmosphere
  • Able to cause extremely cold conditions if its vortex is disturbed or deteriorates
  • Rarely found in inhabited areas, but has moved south like an Arctic cyclone
  • Possibly further south than normal due to a build up of warmer areas in Greenland or Alaska.

More on this story