"The first knowledge they had was when the lightning hit," Capt. Danny Douglas said of his lifeguard crew. In his 30 years as a lifeguard, he had never seen lightning strike a Southern California beach — he'd rarely even seen it rain during the summer.
Other authorities were skeptical of what good broadcasting alerts would do.
"Southern California surfers are Southern California surfers," said Capt. Brian Jordan of the Los Angeles County Fire Department. "Nothing will drive them out of the water."
The storm came out of a front of warm, subtropical air from Mexico that usually doesn't make it as far west as California. When it did, that front collided with the cooler marine layer that normally envelopes Southern California's beaches during much of the year, keeping them cloudy and cool, even during the afternoon.
The result was a ferocious lightning strike and thunderclap that set off car alarms, showered the local lifeguard station with sparks and shook the building.
In more thunderstorm-prone parts of the country, golf tournaments and baseball games have sometimes been delayed when thunderstorms are seen approaching. But, Patzert noted, that never happens in California because lightning strikes don't often happen except in the mountains and deserts.
"The probability of getting hit by lightning in California is one in seven to 10 million, depending on where you live," Patzert said. "In Florida, the lightning capital of the country, it's one in a million."
As people returned by the thousands to Venice Beach on Monday afternoon, some like Laurent Mahuegt of France were counting on those odds holding.
He, his wife and three children had left the beach Sunday just 30 minutes before the storm struck, but they were quickly back in the water.
"If I see dark clouds, I'll leave," he said.