A series of storms that have rolled across California in the past week dumping heavy rain and snow could herald the end of a punishing historic drought, officials said Thursday.

"Bye bye Drought. Don't let the door hit you on the way out," tweeted the National Weather Service in Reno, Nevada, which monitors parts of northern California, the area hardest hit by the storms.

According to the US Drought Monitor, all of northern California is now free of drought but much of the southern part of the state remains dry, with some 30 percent of the region still in extreme or exceptional drought conditions.

"In southern California, we've had the highest rainfall in at least five years and in northern California it's the highest rainfall in at least 10 years," said Tom Fisher, weather specialist for the National Weather Service.

"For example, if you go up to Santa Rosa, which is up in Sonoma County, normally they would have about three inches (7.5 centimeters) of rain for the month so far, and they've had 11 inches," Fisher said, adding that the same scenario was playing out across much of the state.

That's a far cry from a year ago, when practically all of California was reeling from a severe five-year drought that left water reservoirs empty, helped spark huge wildfires and led to severe water restrictions.

Authorities warned, however, that although nature was looking greener and the water reservoirs were filling up, it was still too early to cry victory.

"California's rainy season goes through April, so we're not out of the woods yet," Fisher said.

Ted Thomas, a spokesman for the Los Angeles Department of Water Resources, said he was cautiously optimistic and stressed that the impact of the long drought could not be erased overnight.

"In California, we have a long history of changing weather conditions, in which for example we start with a very wet winter and end up extremely dry," he told AFP.

"This is a very large state and conditions are different in different areas."

The office of Governor Jerry Brown, who proclaimed a drought-related state of emergency in 2014, also said it was too soon to call the drought over.

"It's early in the water season and we know from experience that storms can cease," Nancy Vogel, spokeswoman for the California Natural Resources Agency, told AFP, speaking on behalf of Brown's office.

"The status of reservoirs, snowpack, and groundwater levels at the end of the rainy season will be part of the assessment of the governor's statewide drought emergency declaration."

Meanwhile meteorologists said that following the heavy rain that pounded the southern part of the state prompting flood warnings and landslides, the weather should clear up through next Wednesday when another storm system is expected to bring more downpours.