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: