Motorists sit in gridlocked traffic during a rainstorm that flooded Northbound U.S. Highway 101 on Friday in Cortemadera, Calif.

Sacramento, Calif. ? Howling winds, pelting rain and heavy snow pummeled California on Friday, toppling trees, flipping big rigs, cutting power to more than a million people and forcing evacuations in mudslide-prone areas.

Flights were grounded and highways closed in Northern California as gusts reached 80 mph during the second wave of an arctic storm that sent trees crashing onto houses, cars and roads. Forecasters expected the storm to dump as much as 10 feet of snow in the Sierra Nevada by Sunday.

Highways from Sacramento to San Francisco were closed because of debris or toppled big rigs blocking lanes, and local roads were flooded. Interstate 80 was closed in the Sierra, the main link between Northern California and Nevada.

“A huge tree, over 100 years old, just fell across the house. It just wrecked the whole thing,” said Faye Reed, whose daughter, Teenia, owns the damaged home north of Sacramento. “They won’t be able to live in it. The whole ceiling fell in, and now it’s raining inside.”

More than a million people from the Bay Area to the Central Valley were in the dark. Crews worked to restore power, but it could be days before all the lights are on, said Pacific Gas & Electric spokeswoman Darlene Chiu.

In Southern California, authorities in Orange County ordered an estimated 3,000 residents to evacuate homes in four canyons scarred by wildfires and therefore prone to mudslides.

“It’s too late once the rain starts. These areas are extremely vulnerable. You’re risking your life and your family’s life fundamentally” by ignoring orders, said Steve Sellers of the governor’s Office of Emergency Services.

Flash flood warnings were issued in canyon burn areas in Malibu and in Los Angeles, Santa Barbara and Ventura counties. Riverside and San Bernardino counties, east of Los Angeles, deployed swift-water rescue teams as a precaution. The California Highway Patrol reported flooding in the area.

The state opened its emergency operations center Friday morning to coordinate storm response, and Gov. Arnold Schwarzenegger said he had spoken with Homeland Security Secretary Michael Chertoff by phone.

“Preparation is really the heart of this whole thing,” Schwarzenegger said after touring the state emergency operation center at the Los Alamitos Joint Training Base.

Homeowners in Southern California stacked sandbags and hay bales around their homes while residents in the low-lying areas of the Central Valley piled sandbags to barricade their homes from streams that forecasters warned might swell.

Travelers’ flight plans were put on hold throughout Northern California when airlines delayed or canceled flights. The state Legislature in Sacramento closed offices and sent employees home early.

A wind gust of 125 mph was recorded in the Sierra on Friday afternoon, the National Weather Service said.

The huge storm also toppled trees and cut power to thousands of residents in Washington and Oregon.