Freezing rain and stinging winds slammed the Southwest , covering highways in frost and closing schools and businesses, as millions of residents hunkered down for icy conditions expected to last all weekend.
In California four people died of hypothermia.
Despite warm temperatures earlier in the week, Texas faced the same wintry blast that has hit much of the US with frigid temperatures, ice and snow.
The weather forced the cancellation of today's Dallas Marathon, which was expected to draw 25,000 runners. A quarter of a million customers in North Texas were without power, and many businesses told employees to stay home to avoid the slick roads.
The storm stretched from southern Texas, through the Midwest and Ohio Valley and up into northern New England and the Canadian Maritimes.
Police in Arlington, west of Dallas, reported one driver died when his car slammed into a truck. Authorities in Oklahoma reported two weather-related traffic deaths.
Storms this week had already dumped up to 60cm of snow in Minnesota and Wisconsin and draped many areas in skin-stinging cold. In North Dakota wind chill pushed the temperature to nearly -40C.
- AP