Update 1:15 p.m. Weekend storm improved LA Basin's rainfall picture
The weekend rain brought the Los Angeles basin its most significant precipitation this winter. According to a metric that tracks rainfall in the region, we're now up to over 8 percent of a typical year's total — up from about 4 percent just two days ago.
The numbers come from climatologist David Pierce of the Scripps Institution of Oceanography. He crunches data from 20 rain gauges in the region. The numbers track the 'water year' — the 12-month stretch from October through September that scientists use to understand California's climate.
This number starts at zero each October. If it tops 100 by Sept. 30, the end of the water year, then it's been an above-average year for rainfall.
During La Niña years, rainfall can often underwhelm. Scientists say it's hard to predict how much rainfall La Niña will bring to Southern California this year, but that Northern California is likely to see an above-average year.
Eight percent is decent for late November, according to the historical record — and it's ahead of many previous La Niña years. The chart below shows more context, comparing this year's rainfall to a median and typical La Niña year in Southern California.
Update 10:50 a.m. LA County issues beach bacteria warning after rain
Los Angeles County health officials are advising swimmers and surfers to stay out of the ocean for at least three days because of storm runoff.
The rain advisory issued Monday came as a storm system moved through Southern California after bringing more than an inch of rain in some areas.
Bacteria levels can increase significantly during and after rainstorms as contaminants in the runoff enter the ocean via storm drains, creeks and rivers.
The advisory, customary following heavy rains, is in place through Thursday morning.
8:18 a.m. Storm soaks LA, but it's on the way out
Rain soaked Southern California overnight and into the early morning hours Monday, briefly prompting a flash flood warning for residents living in the Sand Fire burn area in Santa Clarita.
Weather officials said there were no reports of debris flows, which can be a danger in areas recently burned by wildfires, and the warning has since expired.
But the rain fell hard enough to swell rivers, flood some freeways and knock out electricity in some areas.
A swiftwater rescue team pulled four people from an island along the Los Angeles River near Los Feliz Boulevard, Los Angeles Fire Department spokesman Erik Scott told KPCC. At its peak, the water was traveling up to 35 miles per hour in the thickly vegetated area, he said.
The department received the call from the victims themselves at 2:42 a.m. In total, about 100 LAFD firefighters were on scene, with additional assistance form the Glendale and Pasadena city fire departments.
“The [victims] were treated for the exposure to the cold and wet environment and then were transferred to the hospital in fair conditions,” Scott said.
Another man was rescued from the river in South Gate, according to NBC4.
Thunderstorms in northern Orange County briefly knocked out power for hundreds of customers, but electricity has mostly been restored, the Associated Press reports.
About 3/4 inch of rain fell across most of Los Angeles County, with some areas seeing an inch or more, including Van Nuys, Pasadena and possibly Burbank, along with the south-facing foothills of the San Gabriel Mountains, according to Curt Kaplan, a meteorologist with the National Weather Service.
The Getty Center in the Sepulveda Pass received up to 1.3 inches, Kaplan told KPCC.
But the rain is only expected to stick around for a few more hours, according to Andrew Rorke with the weather service.
"Monday we'll still have some showers but they won't add up to much, and the storm should be nothing but a memory by Monday afternoon," Rorke said.
The snow has been falling in the higher elevations, too, where snow chains are required and a winter weather advisory continues until 4 p.m.
A high surf advisory also remains in place for Santa Monica and Venice beaches until 6 p.m.
Temperatures should return to near normal for much of the Thanksgiving week.
This story has been updated.