Article Photos: State-by-state look at frigid blast hitting US 9/36

In this undated photo provided by The North Dakota Petroleum Council is an oil rig surrounded by snow in western North Dakota's oil patch. Some people were choosing to stay indoors as an arctic blast swept across the Northern Plains, but the prospect of temperatures not cracking single digits is just another challenge for the roustabouts, roughnecks and thousands of others working outside who grin and encdure. (AP Photo/North Dakota Petroleum Council)