CNN News:极地旋涡来袭 美国多地迎严寒天气

Outside Alaska, the coldest temperature ever recorded in the U.S. was where? Mount Washington, New Hampshire, Rogers Pass, Montana, Greenfield, Wisconsin, or Cavalier Airport Station, North Dakota. In 1954, the temperature of -70 degrees Fahrenheit was recorded in Rogers Pass.
And this weekend, places like Rogers Pass probably won't see temperatures get above 0 degrees Fahrenheit. Unless you like ice storms, Artic cold and/or rain, it's not looking like a pretty Valentine's weekend for much of the United States. Meteorologists say that pesky polar vortex is to blame.

The low-pressure system usually keeps Artic air bottled up at the North Pole but when it gets unstable in winter, as it is now, the polar vortex allows that air to spill south and then, well cold. Nearly 75 million Americans are under Winter Weather Alerts.
They're spread from coast to coast. There's a rare blizzard warning in Portland, Oregon. And there's a belt of weather advisories stretching from central Texas to southern Connecticut. In the middle of that belt from Arkansas to Kentucky, forecasters are predicting dangerous ice accumulation that can knock out power and damage trees. Temperatures in several areas are expected to break records. Wind chills will make them feel even more harsh.