In 2014, the term “polar vortex” burst on the scene across Canada and the U.S. as temperatures plunged. In some places, it was colder than it was on Mars. Well, get ready to hear more about it.

You’ve almost certainly heard of the polar vortex. But what about "sudden stratospheric warming," a weather term that’s started making the rounds on social media? They’re related to one another, and ...