What’s Causing Freezing Temperatures Across the U.S.?

With temperatures in the teens in Washington D.C., the C&O Canal is frozen solid. So are tens of millions of people from Maine to the Carolinas… "And now to add insult to injury there’s been some of the coldest air in the last couple of decades invading the Northeast from the Arctic," says Dave Robinson, a professor of climatology at Rutgers University. He says what’s behind it all is the polar vortex…"The polar vortex is essentially the coldest air found in the Northern Hemisphere, and it’s situated up in the Arctic in the bulk of the winter," Robinson says. "But occasionally, a lobe of that will dip south above the jet stream and allow that cold air down into the Middle Atlantic states. Sometimes last winter, it was into the northern Plains."