Polar Vortex

Almost the entire US has been experiencing freezing temperatures over the last few days. Over 70% of the country is covered in snow. Hundreds of thousands of people are still without power in Texas, and at least 23 people have died from the storm or its aftermath. Experts–like atmospheric scientist and University of Georgia professor Marshall Shepherd–are placing the blame for these dangerous weather patterns on a phenomenon called the polar vortex. (AP Photo/Charles Rex Arbogast)