Summary (tl;dr)

California is currently being impacted by a powerful "Pineapple Express" atmospheric river storm, bringing widespread flash flood warnings, particularly to Southern California, along with risks of mudslides, strong winds, and isolated tornado threats. Governor Gavin Newsom has declared a state of emergency across multiple counties as the severe weather continues to disrupt holiday travel and poses significant dangers.

Essential Background

California is experiencing a series of powerful winter storms fueled by atmospheric rivers, long, narrow bands of moisture originating from the tropics. These systems bring intense rainfall, strong winds, and mountain snow to the state. Earlier in the week, Northern California was already soaked, leading to saturated soils and heightening the risk of flooding and landslides as the storm system moved south.

The Full Story

As of December 24, 2025, Southern California is bracing for, and experiencing, the most severe impacts of the storm, which forecasters are calling one of the worst Christmas storms in recent memory. Flash flood warnings are in effect for large portions of Los Angeles, Ventura, Santa Barbara, and San Bernardino counties, with a high risk of life-threatening flooding. Heavy rainfall rates, potentially exceeding one inch per hour, are expected, especially over favored south-facing slopes. This has led to an increased threat of mudslides and debris flows, particularly in areas recently scarred by wildfires, such as the Altadena, Palisades, and Eaton Fire zones.

A tornado warning was briefly issued and subsequently canceled for parts of east-central Los Angeles County, including Alhambra, Rosemead, and Monterey Park, amid severe thunderstorms. While rare, there is a continued risk of isolated tornadoes along the northern coast and in the Central Valley due to unusual atmospheric conditions. Governor Gavin Newsom has proclaimed a state of emergency for Los Angeles, Orange, Riverside, San Bernardino, San Diego, and Shasta counties to facilitate rapid mobilization of state resources. Numerous communities are facing evacuation orders and warnings, and roads, including sections of Highway 18 and Highway 101, are experiencing closures due to flooding and slides.

Why It Matters

This severe weather event is causing significant disruptions and posing life-threatening risks across California during a major holiday travel period. The combination of saturated ground and ongoing heavy rain creates a high potential for widespread flash flooding, dangerous mudslides, and debris flows, particularly threatening communities near recent burn scars. The state of emergency allows for critical resource allocation and support to local governments for emergency response and recovery efforts. Travelers are urged to avoid roads due to hazardous conditions, including potential road closures, downed trees, and power lines, highlighting the serious implications for public safety and infrastructure.

Geographic Location

• Los Angeles County, California, United States (widespread flash flood warnings, brief tornado warning, mudslide risk in burn scar areas including Altadena, Long Beach, Downtown L.A., Inglewood, Alhambra, Torrance, Culver City, Hollywood, Griffith Park, Hermosa Beach, Manhattan Beach, Whittier, Redondo Beach, Beverly Hills, Pasadena, Venice, Rancho Palos Verdes, Santa Monica, West Covina, Lake Los Angeles, Acton, Palmdale, Lancaster, Santa Clarita, Quartz Hill, Pearblossom, Llano, Littlerock, Lake Palmdale, Elizabeth Lake, Lake Hughes, Valyermo, Desert View Highlands, Saddleback Butte State Park, Altadena burn zone, Palisades burn scar, Eaton Fire burn scar, Sun Valley flooding, Thousand Oaks, Simi Valley, Malibu, Woodland Hills, Santa Clarita, Sylmar, Alhambra, Rosemead, Monterey Park)
• Ventura County, California, United States (flash flood warnings, severe thunderstorm warning, mudslide risk)
• Santa Barbara County, California, United States (flash flood warnings, severe weather events, road closures near Gaviota State Park)
• San Bernardino County, California, United States (flash flood warnings, mudslide/debris flow near Wrightwood, SR-18 closure)
• Orange County, California, United States (state of emergency, evacuation warnings for burn scar areas)
• Riverside County, California, United States (state of emergency)
• San Diego County, California, United States (state of emergency)
• Shasta County, California, United States (state of emergency, heavy rain, flash flooding, water rescues, one death)
• Sacramento Valley, California, United States (flood watch, high wind warning)
• San Francisco Bay Area, California, United States (flood watch, high wind warning, risk of thunderstorms and isolated tornadoes, localized flooding)
• Sierra Nevada, California, United States (heavy snow, blizzard conditions, high winds, near white-out conditions)
• Death Valley, Inyo County, California, United States (flash flood warning, rocks and debris on Highway 190)