Over 20 dead in US polar vortex, frostbite amputations feared

Heavy snow hitting Chicago off the Great Lakes was set to begin winding down on Thursday night, the weather service said.

More than 30 record lows were shattered across the Midwest.

Cotton, Minnesota, had the lowest national temperature recorded early on Thursday at minus 56 F (minus 48 C), before the weather warmed up, the weather service reported.

Temperatures in the Upper Midwest will rebound to well above zero F (minus 18 C) on Friday, with highs making it into the teens and low 20s F. By Saturday, highs will be in the 30s and even low 40s F, while the central Plains will be in the low 60s F, nearly 20 to 25 degrees above normal, the weather service said.