A so-called polar vortex is blasting much of the United States, with swaths of the country set to record some of their lowest temperatures in decades. Wind chills are projected to drop as low as -70 degrees Fahrenheit in the Midwest. The National Weather Service called the blast “historic and life-threatening,” warning the wind chills are cold enough to freeze human flesh within five minutes. Below-zero temperatures were predicted as far south as Alabama, with nearly half the country set to plunge below freezing by Wednesday. Indianapolis Mayor Greg Ballard warned residents to take precautions.

Mayor Greg Ballard: “This weather combination that we’re seeing right now with all of the snow and the cold is unlike anything that we’ve seen in decades in this area, and I can’t emphasize that enough. The cold really scares me, and as such that we will have temperatures that are potentially deadly or certainly life-altering temperatures right now, and we have to be very, very careful with that.”

The cold blast comes after at least 16 people died from a winter storm that brought snow and freezing temperatures to the Midwest and Northeast.