LOS ANGELES, Feb 25 ― A slow-moving winter storm intensified over California yesterday, triggering the first blizzard warning in parts of the Los Angeles area in 30 years and creating the extraordinary sight of snowflakes swirling around the iconic Hollywood sign.

Snow and freezing rain pushed into the Golden State from the north, where it dumped about 10 inches (25 cm) of powder on Portland, Oregon, earlier in the week. California's snow was heaviest in the Cascades, Sierra Nevada and coastal mountains.

But even residents in lower-elevation foothills of California's central coast and the San Francisco Bay area awoke Friday morning to 1 to 3 inches of snow.

"The last time we saw snow like this in the low elevations was in 2011,” said Sarah McCorkle, a National Weather Service (NWS) meteorologist in Monterey, California. "It's a relatively rare event.”

San Francisco also broke a 132-year record for the lowest February 24 temperature ever documented as the mercury dipped to 39 degrees Fahrenheit (4 Celsius) on Friday morning, one degree lower than the previous record set in 1891, McCorkle said.

The storm was expected to strengthen on Friday and linger over California through Saturday, the NWS said.

A massive low-pressure system driven from the Arctic was responsible for the unusual conditions, said Bryan Jackson, a forecaster at the NWS Weather Prediction Center in College Park, Maryland.

In Southern California, "this is a rare case of a cold, significant storm event,” Jackson said.

In a sight that must have delighted many Angelenos, snowflakes even fell around the Hollywood sign atop Mount Lee in the hills above the city, known for its sunny days and palm trees.

At an elevation of 1,500 feet (457 metres), the sign ― with its giant, white-block lettering visible for miles around the city ― was close to the threshold for the formation of snow during the storm, Jackson said.

Craig Robert Young, an actor who starred in the television series Charmed and The Last Ship, lives in Hollywood Hills within eyeshot of the famed sign. He said he was amazed to see snow swirling there.

"I moved here from the UK 20 years ago, and haven't seen snow since,” said Young, 46. "I actually had a snowball fight. It brought me back to my childhood.”

In nearby San Bernardino County, the sheriff's office posted a video clip on Twitter showing deputies lying in the snow, flapping arms and legs to make "snow angels,” while also urging residents to stay off roads.

‘At the mercy of the skies’

Snowy road conditions and high winds prompted the California Highway Patrol (CHP) and state transportation officials to close Interstate 5, a major highway connecting Los Angeles to points north, along a 40-mile (64.4 km) mountain stretch known as the Grapevine.

It remained unclear how long the closure would last, according to CHP officer Anthony Daulton.

"We're at the mercy of the skies right now,” he said.

A separate storm that clobbered the US Plains, Midwest and Great Lakes regions earlier this week blew out to the Atlantic on Friday after passing over New England, the weather service said. More than 750,000 homes and businesses, mostly in Michigan, remained without electricity.

Even before the latest storm, much of California has experienced an unusually rainy, chilly winter, starting with a spate of deadly "atmospheric river” storms that unleashed widespread flooding, felled trees and triggered mudslides in a state long plagued by drought and wildfires.

Powerful winter storms, interspersed with extreme heat and dry spells, are symptoms of climate change, experts say, and growing more frequent and intense.

In Los Angeles County yesterday, a blizzard warning was issued for the San Gabriel Mountains north of the city ― the first in the L.A. region since 1989 ― with 2 to 5 feet (60 to 152 cm) of snow forecast above an elevation of 4,500 feet (1,370 metres), the weather service said. Seven feet (2.1 metres) of snow could accumulate in some spots with winds gusting up to 60 miles per hour (96 kph).

Big Bear Lake in San Bernardino County already has 28 inches (71 cm) of snow on the ground, Jackson said ― and more was coming.

Drenching rains posed a different problem across wide swaths of Los Angeles and Ventura Counties, where a flash flood warning was posted until 10 p.m. Friday night.

Heavy showers will inundate many parts of California through Saturday, the weather service said. Two to 3 inches (5 to 7.6 cm) are forecast for Los Angeles and San Bernardino, raising the risk of flash flooding.

More than 120,000 California homes and businesses, primarily in the northern part of the state, were without power yesterday, according to Poweroutage.us. ― Reuters