A powerful atmospheric river drenched Southern California with 2 to 13 inches of rain between Thursday and Monday, shattering decades-old records and marking the wettest November in 40 years for Los Angeles.
Downtown Los Angeles recorded approximately 2.8 inches through Monday, while foothill communities and reservoirs in the San Fernando Valley received 4 to 6 inches or more during the five-day deluge. Mount Wilson in the San Gabriel Mountains picked up almost 5 inches, and preliminary National Weather Service gauges in the high country measured upward of 7 to 8 inches at the wettest spots.
The intense rainfall broke daily records in multiple locations. Downtown Los Angeles surpassed a 1952 record Saturday with 1.65 inches in 24 hours, edging past the previous mark of 1.64 inches. The National Weather Service reported that its Oxnard office and Santa Barbara Airport also shattered long-standing single-day November records.
By Sunday morning, downtown LA's monthly total reached 2.57 inches, exceeding any November since 1985. The deluge put November 2025 on track to rank among the wettest on record, far above the 0.78-inch long-term average for the month.
The storm's runoff rapidly filled local rivers, flood control basins and reservoirs, testing the county's water management infrastructure. Los Angeles County's 14 major dams captured the bulk of stormwater, preventing widespread flooding while adding significantly to local water supplies.
"The first major storm of the season produced over three inches of rainfall in parts of LA County, adding more than 700 million gallons to local water supplies," the County Department of Public Works noted after an October system. This mid-November event likely contributed an even greater volume.
Engineers will gradually divert billions of gallons of captured stormwater into 27 spreading grounds, where water soaks into the earth to recharge vital underground aquifers. The county's flood-control network of 491 miles of open channels, 3,400 miles of storm drains and 189 debris basins played a critical role in protecting communities while conserving rainfall.
However, the deluge prompted health concerns at the coast. The Los Angeles County Department of Public Health issued an Ocean Water Quality Rain Advisory covering all county beaches through at least 8 a.m. Wednesday. Officials warned residents to avoid contact with ocean and bay waters for at least 72 hours after rainfall stops due to contamination from storm runoff carrying bacteria, chemicals, trash and debris.
Exposure to contaminated water can cause skin rashes, ear infections, fever, nausea or gastrointestinal illness, according to county health officials.
Meanwhile, Caltrans crews Tuesday reopened the 3.6-mile stretch of Topanga Canyon Boulevard between Pacific Coast Highway and Grand View Drive that closed Thursday night due to rainstorms, rockfall and debris flows. The highway reopened shortly before noon after workers cleared mud and debris from Monday night's additional storms.
The stretch remains an active work zone for ongoing recovery efforts from the Palisades Fire and winter storms, with nightly closures from midnight to 5 a.m. and traffic restrictions including a half-mile, one-way traffic control section.
Forecasters warned more rain is expected Thursday through Friday, with the National Weather Service predicting another 0.5 to 1 inch across many areas and up to 2 inches in the foothills.