This Is The Clearest Picture Of How Arctic Temperatures Are Spreading To America

This is the best image we've seen of how the "polar vortex" has infiltrated the U.S., causing the cold snap we are experiencing. Blue is the freezing line: The image above was tweeted out by AccuWeather's Anthony Sagliani. He created it using the Living Earth app (available for iPhone, iPad and Mac). SEE ALSO: Here's What The 'Polar Vortex' That's Hitting The US Actually Is SEE ALSO: CHART: Here's How Long You Can Stay Outside In Extreme Cold Temperatures Before Getting Frostbite Join the conv...