LOS ANGELES -- After four years of a historic drought, scientists in California are through relying on nature alone for help.

Rainfall like the area has had over last few days is so rare in Southern California that Los Angeles County is hoping to squeeze out every drop -- by cloud seeding.

"There are 10 of these locations throughout the San Gabriel Mountains," said Kerjon Lee of the L.A. County Department of Public Works.

The DPW has paid a half million dollars to a cloud seeding contractor promising to make more rain. Lee says it's not just hocus pocus.

"This actually comes with a lot of science behind it," Lee told CBS News.

Cloud seeding works when silver iodide particles are sprayed into a saturated cloud. They act like a nucleus, which attracts super-cooled water vapor that freezes into ice. Once the ice becomes heavy enough, it falls and melts to become rain.

A graphic illustrates how cloud seeding works. CBS News

"It is wishful thinking," said Graeme Stephens, who studies clouds and weather systems for NASA.

"It's been shown under certain circumstances it works but in a very marginal way," Stephens said. "And even then, it would be difficult to prove how much increases actually occur."

L.A. County officials insist they can get up to 15 percent more rainfall, with no health risks. Lee said the process will not contaminate the water supply.

"No, absolutely not," he said. "Cloud seeding is absolutely safe."

And he said it could make a big difference.

"Based on our 50-year study, I think we can get an additional 1.5 billion gallons a year," Lee estimated.

That would be a welcome sight in Southern California's depleted reservoirs.