Storms packing heavy snow and hurricane-force winds left tens of thousands without power in the United States and wreaked havoc for people travelling for the Thanksgiving holiday.

On one of the country's busiest travel days of the year with an estimated 55 million people planning to drive or fly, highways in the west and midwest were closed because of snow, and hundreds of flights were cancelled.

There are also fears the giant, colourful character balloons floating through Manhattan during the Macy's Thanksgiving Day Parade might be grounded for today's festivities because of gusting winds in the Big Apple.

"An extremely active weather pattern is in place across much of the US," the National Weather Service said.

A snow storm that caused near white-out blizzard conditions in Colorado dumped a foot of snow in Wyoming on Tuesday, and was barrelling eastward toward the Great Lakes region in the central US.

Ploughs worked through the night at the airport in Minneapolis.

Denver International Airport was hit with 30cm of snow and nearly 500 flights were cancelled and another 500 were delayed.

A dangerous storm hit southern Oregon and northern California that meteorologists are calling a  "bomb cyclone" - a rapidly intensifying winter storm caused by a precipitous drop in atmospheric pressure. 

"The drop typically creates violent weather that arrives like a bomb going off," The Oregonian newspaper said.

It dumped around 30cm of snow, forced roads to close and prompted warnings for people to just stay home.

A police officer assists a motorist who skidded off a road in Iowa

One wind gust Tuesday in Lake Tahoe, Nevada was clocked at 155km/h.

The US Northwest has not been hit by such a powerful storm since 1962, said Marc Spilde of the National Weather Service.

"This storm threatens to bring rain and mountain snow to much of California, including places like San Francisco and Sacramento, places that were largely spared by the past week's rain," said Accuweather senior meteorologist Brian Thompson.

A silver lining was that rain doused the Cave Fire in Santa Barbara County, which burned 1,810 hectares of brush and woodlands.

 But it brought evacuation warnings to thousands of residents in Santa Barbara suburbs for possible mudslides on fire-charred hills.

The National Weather Service said while the two separate storms are expected to weaken today, holiday travel would be affected through the weekend.

Passengers queue at check-in desks at O'Hare International Airport, Chicago

It also warned of the potential of flash floods in southern California through today because of heavy rain.

The storms and high winds left nearly 300,000 people without power across five states, including Michigan, Ohio and Wisconsin, though nearly half had power restored by yesterday evening, according to poweroutage.us, a utility tracking site.

The nasty weather and blizzard conditions have also forced the closure of major travel routes, including Interstate 5, the main thoroughfare from Oregon into California.

Motorists on the highway reported being stuck for hours on the road overnight, with some having to sleep in their cars.

In Arizona, the National Weather Service said it expected travel conditions to be "difficult to impossible" from late afternoon through to tomorrow morning.