The Los Angeles Times reported experts suspect a massive fish die-off in the Salton Sea -- actually a lake -- was the source of the foul odor that wafted from Santa Clarita to Riverside, and Ventura County to Palm Springs.
Kathy Gray in Santa Clarita said it smelled like a broken sewer pipe. Chris Tatum thought something was burning.
"It reeks," he said. "It smells like rotten mush."
It was so bad people were tying up emergency lines and health officials started checking for a toxic spill or sewage plant leak, the Times said.
Officials said they believe thunderstorms and 40 mph winds Sunday churned up the waters of the Salton Sea and sent the dead-fish odor up to 100 miles west overnight, the Times said.
"It's very unusual that any odor would be this widespread, from the Coachella to Los Angeles County," said Sam Atwood, spokesman for the South Coast Air Quality Management District. "We're talking well over 100 miles. I can't recall ever confirming an odor traveling that distance."
Bill Meister, president of the Sea and Desert Interpretive Association, agreed the stiff winds could have done the trick.
"Because the lake is so shallow, and there is 100 years worth of decayed material at the bottom, you'd get that rotten egg smell."
Andrew Schlange, general manager of the Salton Sea Authority, extreme heat the past several days could have killed off fish that sank to the bottom where they decomposed with other organic material, then when the storms churned up the water, up came the odor.