At least six deaths are blamed on a wintry storm that's pushing through the Rockies and Midwest, bringing bitterly cold temperatures and treacherous driving conditions.
The cold weather is also threatening crops as far south as California.
Forecasters say the wind chill could drop to 30 degrees below zero in parts of Montana today. Wind chills of minus 20 have already been recorded in the Nebraska Panhandle.
Lows in the Denver area are expected to drop below zero over the next several days.
The storm has spread about 2 feet of snow in northeastern Minnesota, contributing to hundreds of traffic accidents, at least four of them fatal.
Fatal crashes have also been reported in Montana and North Dakota.
The icy blast is expected to be followed by another later in the week, creating an extended period of cold weather that hasn't been seen since the late 1990s. Forecasters say the jet stream is much farther south than normal, allowing cold air to push in from the Arctic.
As it pushes south, the cold could bring near-record low temperatures to parts of California and endanger citrus crops in the Central Valley.