Meteorologists claim that the deadly cold weather has brought what they call, a “once-in-a-generation” deep freeze to several US states, causing schools to be shut down. The US Postal Service has also cancelled mail deliveries to the region on Wednesday. The powerful polar vortex has already been blamed for at least 6 deaths, that recently occured in Illinois, Iowa, Indiana, Wisconsin and Minnesota.

“These are VERY DANGEROUS conditions and can lead to frostbite on exposed skin in as little as five minutes where wind chill values are below -50,” the National Weather Service office near Minneapolis and St. Paul tweeted, according to CNN. “Best thing you can do is limit your time outside.”

“A state of emergency has been declared in the Midwestern states of Wisconsin, Michigan and Illinois, as well as southern states of Alabama and Mississippi,” BBC reports. According to the National Weather Service, “temperatures across the Midwest on Wednesday were colder than the likes of Greenland and Alaska.”