A powerful snowstorm socked the upper Midwest on Saturday with as much as 20 inches of snow, forcing authorities to close roads across five states as heavy winds made for treacherous driving conditions.

The snowstorm was expected to be followed by dangerous cold. North Dakota experienced wind chills of 20 degrees below zero, and the arctic air was expected to drop temperatures below zero by Sunday night throughout the Dakotas and in parts of Iowa, Minnesota and Wisconsin.