The jet stream is much farther south than normal,Cheap Adidas Shoes
, allowing the cold air to push in from the Arctic and drop temperatures by 20 to 40 degrees below normal levels, AccuWeather meteorologist Tom Kines said.
Areas of Montana and the Dakotas were forecast to reach lows in the minus-20s, while Laramie, Wyo. is expected to see a low temperature of 28 below. The icy arctic blast was expected to be followed by another one later in the week, creating an extended period of cold weather that hasn't been seen since the late 1990s, meteorologists said.