This polar vortex graphic is the most upsetting map of the winter

Just how bad was this winter? Bad. Really, really bad as this terrifying visualization of global temperatures during these last few months shows.

Top image: Visualization of the polar vortex this winter / NASA's Goddard Space Flight Center with video and images courtesy of NASA/JPL

NASA put together this look at the record-breaking cold temperatures it's been monitoring this winter using infrared sensor 3,000 feet above the earth's surface. As you can see, we began December with a pretty normal polar vortex lingering over top of Canada and the Arctic. Things started to unravel in late December, and by early January, there's a single line of arctic air stretching straight from the North Pole clear down to Florida.

So what happened to cause it all? NASA scientist Eric Fetzer explains how a low pressure system in Canada's Hudson bay and an unusual movement of the jet stream conspired to drop temperatures in this video: