A man (20) has died after lightning struck 14 people during thunderstorms that have swept through Southern California in the United States.

The man was taken from Venice Beach in Los Angeles and pronounced dead at a hospital on Sunday afternoon, the Los Angeles' County Coroner said.

A total of 13 people were treated after they were struck by lightning at Venice Beach. Four were treated at the scene and released, and the rest - including a 15-year-old - were taken to hospital.

Los Angeles Fire Department spokeswoman Katherine Main said one of the individuals was considered critical while the others were said to be in "fair" condition. Some of the injured were in the water and others on the busy beach's famed boardwalk at the time of the strikes.

The Los Angeles County Sheriff's Department said a fourteenth person was struck on a golf course on Southern California's Catalina Island.

The man (57) is reported to be in a stable condition.

Witnesses described scenes of panic as the sky darkened and lightning erupted shortly afterwards, with thunder and rain. "You could hear everybody screaming" Angelica Roquemore told the Los Angeles Times.

Roger Davis was quoted by the newspaper as saying that his house shook and that he heard explosions.

When he ran outside, his neighbour - a doctor - was administering CPR to a victim, he told the paper.

Authorities say the thunderstorms also sparked at least two small grassland fires on the island that were quickly put out. The unusual weather comes from monsoon moisture that has brought thunderstorms, experts say.

These witnesses describe what happened.