SAN FRANCISCO » A powerful storm churned down the West Coast on Thursday, bringing strong gales and much-needed rain and snow that caused widespread blackouts in Northern California and whiteouts in the Sierra Nevada.

The brunt of the storm hit the San Francisco Bay Area, flooding freeways, toppling trees and keeping thousands of people home from work and school.

"It’s a big storm, as we expected, and it’s headed south with very powerful winds and heavy rainfall," said National Weather Service meteorologist Will Pi.

In Oregon, strong winds felled a tree, killing a homeless man who was sleeping on a trail, and a teenage boy died after a large tree fell on the vehicle in which he was riding, causing it to swerve and hit another tree.

A huge gust blew down an 80-foot fir at a Santa Cruz elementary school, pinning a sixth-grader by the arm for 15 minutes until chain saws cut him free.

"Unexpected, very unexpected," said the head of Gateway Elementary, Zachary Roberts, who closed the school as the boy was treated and released from a hospital.

This "Pineapple Express" storm carried warm air and vast amounts of water in a powerful current stretching from Hawaii to the mainland and up into the mountains, where gusts up to 140 mph blew through passes, damaging homes in the Lake Tahoe area.

The current left San Francisco drenched but balmy, with 60-degree temperatures, about 5 degrees above average for this time of year.

Waves slammed onto waterfronts around the Bay Area, ferries were bound to their docks, airplanes were grounded and many schools and businesses told people to stay home.

The gusts made motorists tightly grip their steering wheels on the Golden Gate Bridge, where managers created a buffer zone to prevent head-on collisions by swerving cars.

The iconic suspension bridge is engineered to swing in cross winds, so "the concern we have right now is more about vehicles," spokeswoman Priya David Clemens said.

Sonoma County authorities recommended that hundreds of people evacuate at least 300 homes in the lowest lying areas near the Russian River, which was expected to start overflowing overnight. Peak flooding in the towns of Guerneville and Monte Rio was anticipated by 10 a.m. Friday, forecasters said.

Authorities warned of minor flooding along the Sacramento River in Tehama County and Cache Creek in Yolo County.

Pacific Gas & Electric Co. crews worked to restore power to 110,000 people, down from 166,000 earlier Thursday, with the largest concentration of 7,400 customers in San Francisco, the utility said. The utility’s online map showed lights out over thousands of square miles, from Humboldt near the Oregon border to Big Sur on the Central Coast.

In San Jose, the roof of a grocery store partially collapsed, exposing a 50-square-foot hole above the produce section. One person suffered a minor injury but details were not immediately available, the San Jose Mercury News reported.

There were multiple accidents on flooded roads, and several trees crunched cars. Interstate 5, California’s critical north-south thruway, was closed by flooding in the northern town of Weed. In Marin County, heavy rains washed out a portion of state Route 1, the San Francisco Chronicle reported.

"A lot of people took the day off," CalTrans spokesman Bob Haus said. "That’s a good thing."

Disembarking from a ferry in San Francisco, Malcolm Oubre said some people were overreacting.

"I know it’s a big storm supposedly, but they’re treating it like it’s a hurricane," he said.

Teenagers drove trucks through a flooded Safeway parking lot to make waves for kayakers in Healdsburg as grocery shoppers trudged through several feet of water to get supplies.

East Coast kids revel in snow days, but closures are rare on the West Coast, so Thursday’s canceled classes were a novelty in San Francisco, Oakland, Berkeley, Sonoma and Santa Cruz County.

Surfers welcomed big, choppy swells from the same high seas that sent towering sprays of water airborne along breakfronts in San Francisco and Monterey.

Ski resorts in the northern Sierra Nevada — where schools and roads were closed by whiteout conditions and power outages — were hoping for 3 feet of snow once it all settles.

While rains were expected to continue through Friday evening across much of California, California’s farmers would need more storms this size to even begin to recover from a record drought.

The storm was spreading into Southern California, areas that have suffered wildfires were preparing for mudslides.

Denise George, who sells boats in Marina Del Rey, worried mostly about the wind.

"We make sure the halyards are secure, the canvasses are fastened so nothing gets blown off or opened up, so yes we are battening down the hatches for sure."