A severe winter storm in the US that has seen record amounts of snow fall is set to continue, forecasts say.Blizzard warnings are still in place for parts of North Dakota, South Dakota, Nebraska, Wyoming, Minnesota, Iowa and Wisconsin.
The storm has already dumped 14in (35cm) in Oklahoma City - 11.5in more than the previous record snowfall.
Icy roads had been blamed for at least 21 deaths since the storm hit a few days ago.
Drivers in Minnesota reported brief white-out (zero visibility) conditions, and while some managed to continue to their destinations, others were stuck either in their cars or accommodation as the snow made roads impassable.
In Texas, volunteer fire-fighters and sheriff's deputies rescued hundreds of people stranded along Interstate 44 and Texas State Highway 287 near Wichita Falls.
Thirteen inches of snow fell in the area, a National Weather Service meteorologist said
"It's really been horrible," Wichita County Sheriff David Duke said.
"Although we live in north Texas and get a lot of cold weather, we weren't prepared for the significant amount of snow that we've received."
Interstate roads were also closed in North Dakota, Nebraska and Wyoming.
Snow drifts and strong winds could cause further whiteouts, meteorologists warned.
Flights were cancelled, including at Sioux Falls Regional Airport, Rapid City Regional Airport and Pierre Regional Airport.
The Will Rogers World Airport in Oklahoma City, Oklahoma's largest airport, was not expected to fully reopen for another two to three days.
National Weather Service meteorologist Kevin Kraujalis said the strong winds were producing snow drifts as deep as 5ft.
"It's awful, it's just awful," he told AP news agency.
"It's a big workout just walking outside to check my weather equipment."
