Californians more used to flip flops and shorts were wrapping up warm Thursday as a rare winter blizzard -- the first in more than 30 years -- loomed over Los Angeles, even as the US East Coast basked in summer-like temperatures.

Up to seven feet (2.1 meters) of snow were expected to hit hills around LA, the National Weather Service (NWS) said, as it warned of "extremely dangerous mountain conditions."

A blizzard warning, in effect from Friday morning, is the first one forecasters have raised in the area since 1989.

"We are still on track for our DANGEROUS winter storm. Expect blizzard conditions in the mountains with FEET of snowfall. A few inches of rain are expected in lower elevations. Be weather ready!" NWS Los Angeles tweeted.

While downtown Los Angeles was not expected to see any of the white stuff, there are plenty of mountains nearby.

On a clear day the 10,000-foot Mount San Antonio and other peaks in the San Gabriel Mountains are visible, and their snow-capped tops should offer a pretty sight to city dwellers.

But for those trying to travel over mountain passes, it will be a different matter.

"Areas above the snowline will likely see a combination of strong winds and heavy snow," the NWS in Hanford said.

"Travel will be difficult to near impossible during the passage of the cold front, especially over the mountain passes."

In the Sierra, where storms in January left a voluminous snowpack, more was expected, along with plummeting temperatures.

"Bundle up because it will be cold and windy!" forecasters said.

"Wind chills will be dangerous at times in exposed areas of the high Sierra, plunging as low as -30 degrees (Fahrenheit, -34 Celsius)."

- 'Not good...' -
Other more winter-hardened parts of the country were also getting hit Thursday, with the area around the Great Lakes suffering power outages.

More than 900,000 customers in the region were in the dark around 2300 GMT, according to poweroutage.us.

Forecasters had warned that ice forming on power lines would make them vulnerable to damage in gusting winds.

Local media in Van Buren County, Michigan, reported that a volunteer firefighter was killed by a downed power line.

NWS Twin Cities posted a picture of deep snow drifts outside their office, and warned drivers to take care.

"The drifts on our office sidewalk are around 20 to 24 inches. With the average car's ground clearance being 6 to 9 inches, can you imagine running into one of these going 45+ MPH on the road? Not good..."

The heavy weather was heaping misery on travelers, with more than 1,100 flights within, into or out of the United States cancelled, according to flightaware.com.

Hundreds of schools in the region were closed because of the weather.

The northeast was also under a winter storm warning on Thursday, with difficult traveling conditions in parts of New York state, including Buffalo, where a powerful December blizzard left dozens dead.

But further down the coast, some areas were basking in record-breaking temperatures.

Temperatures around the nation's capital hit 81 degrees Fahrenheit.

"Record high temperatures were broken today at Reagan National Airport and Baltimore Washington International Airport," NWS Baltimore-Washington tweeted.