Severe storms pummel California

A series of thunderstorms that have barreled through California since the New Year's weekend have killed at least two people, knocked out power for tens of thousands of people and threatened much of the state with flash flooding.

"We anticipate that this may be one of the most challenging and impactful series of storms to touch down in California in the last five years," Nancy Ward, the new director of the California Governor's Office of Emergency Services, told The Associated Press.

According to the National Weather Service, the hazardous winds, snow and rain forecast on the West Coast is expected to continue through at least Jan 13-19.

A 2-year-old boy was killed Wednesday evening when a tree crashed through the roof of his family's mobile home in Occidental, "pinning or landing" on top of him, according to NBC News, which quoted a spokesperson from the Sonoma County Sheriff's Office.

The boy's father and mother were home at the time, but they did not report any injuries.

A 19-year-old woman in Fairfield was killed on Wednesday morning while traveling through a partially flooded road. She lost control of her vehicle when it hydroplaned and crashed into a utility pole.

"Unfortunately, speed unsafe for conditions was likely the primary reason for the collision, with water on the road being a contributing factor," the Fairfield Police Department said in a statement.

The severe thunderstorms prompted California Governor Gavin Newsom to proclaim a state of emergency Wednesday.

"California is mobilizing to keep people safe from the impacts of the incoming storm. This state of emergency will allow the state to respond quickly as the storm develops and support local officials in their ongoing response," Newsom said.

Janisse Quiñones, senior vice-president of electric operations at PG&E, told reporters Thursday that the state has received about 15 inches of rain since the storms hit, which created "a very critical situation" for the company's response efforts.

"We are expecting a storm on Saturday and another storm system Monday, which creates window of opening for restoration, (which is) very limited for our crews," she said.

On Thursday, at least 100,000 California residents were without power, according to poweroutage.us.

The powerful storms hitting California are triggered in part by the so-called atmospheric rivers, or long, flowing regions of the atmosphere that transport water vapor through the sky. When atmospheric rivers make landfall, they often release this water vapor in the form of rain or snow.

The US Drought Monitor said Thursday that the heavy rain caused portions of California and Nevada to be removed from the "exceptional drought" status, which is the most-intense drought level.

"The wettest 10-day period for Downtown San Francisco since 1871! Downtown San Francisco received 10.33" Dec 26-Jan 4 (yesterday). All time 10-day record was 14.37" in Jan 1862," the National Weather Service Bay Area tweeted Thursday.