U.S. temperatures at 7 a.m. Tuesday.
What cold weather looks like
With a polar vortex bringing frigid temperatures to the United States, officials warn residents to stay inside or risk frostbite. Here's the National Weather Service's temperature map at 7 a.m. Tuesday, and what that cold snap looked like in different cities across the U.S. Got a photo of the cold? Post it on Instagram with the tag #coldsnaps.
SOURCES: National Weather Service, Instagram.