Paramedics and police were called near the San Gabriel River in Pico Rivera around 8:50 a.m.
The city manager says a woman was found dead on the path with her two dogs. She had apparently been struck by the lightning as storms moved through Southern California in the morning.
The city was warning residents in the area to stay inside until the storm passed, Carmona said.
News of the tragedy was disturbing to residents in the area.
"I'm scared," said Mary Perez, who lives in the area. "I told my granddaughter and her friend, she's not walking to school, I'm taking her. I think more about the lightning. Not that I never thought about it. I didn't think it could really do that. It's just awful."