Northern California is bracing for a powerful atmospheric river event that is expected to bring significant rainfall, warm temperatures, and flooding risks to large parts of the state through the end of the week. On February 23, 2026, the National Weather Service (NWS) issued flood warnings and advisories as the Pineapple Express system moved through the region, disrupting travel and prompting safety concerns.
What is an Atmospheric River?
An atmospheric river, often described as a “fire hose of moisture,” is a narrow band of concentrated moisture in the atmosphere that can carry as much water as the Mississippi River. In this case, the Pineapple Express, a type of atmospheric river originating near Hawaii, has intensified as it tracks eastward across the Pacific and makes landfall in California. The system is expected to bring heavy rainfall, high winds, and mild temperatures, raising concerns about both flooding and avalanches in the Sierra Nevada.
These events are relatively common during California’s winter months, but when they combine with already saturated soils and melting snow from earlier storms, the risk of flash floods, mudslides, and rockslides significantly increases.
Rainfall, Flooding, and Snowmelt Risk
As the storm progresses through the Bay Area and Sacramento Valley, rainfall totals of 1–3 inches are expected in most lowland areas, with some mountainous regions receiving even higher totals. These amounts are enough to overwhelm storm drains, particularly in urbanized areas such as San Francisco and Oakland, where street flooding could disrupt traffic and daily activities. As temperatures rise, the rain will also trigger rapid snowmelt in the Sierra Nevada and mountainous areas, potentially contributing to rising river levels and the threat of riverine flooding.
The NWS has issued warnings for localized flooding, particularly in areas with poor drainage systems. Travelers and residents are urged to avoid driving on flooded roadways, and people living in flood-prone areas are being advised to prepare for possible evacuations.
Winds and Avalanche Threat
Along with heavy rain, the atmospheric river is also bringing strong winds, especially to coastal areas. Gusts up to 60 mph have already been recorded along the coastline, and these winds are expected to continue through the duration of the storm, affecting travel, especially along highways like U.S. 101 and Interstate 5.
For those in mountainous regions, the storm has raised concerns about avalanches. Areas in the Sierra Nevada and Central Coast mountains are under high avalanche danger warnings due to a combination of fresh snow, rain, and high winds, which can destabilize the snowpack. Authorities are advising against backcountry activities in affected regions, and ski resorts are limiting access to certain slopes.
Power Outages and Travel Disruptions
As the storm continues to develop, power outages are a significant concern. High winds, coupled with saturated soils from previous storms, have already caused tree branches to snap and power lines to go down in some areas. Over 500,000 customers in the Bay Area and Central Valley have been warned that they may experience power disruptions, particularly in rural or mountainous regions.
In addition to potential power outages, air travel is likely to be affected as low visibility and high winds will make flying dangerous. As of February 23, major airports, including San Francisco International and Oakland International, have reported hundreds of flight cancellations. Travelers are advised to check with airlines for updates and to plan for potential delays.
On the ground, highways and roads are also expected to be impacted, particularly in the North Bay and Central Coast areas. Many roads could be closed temporarily due to flooding or debris flows, while mountain passes could be inaccessible due to snow and low visibility.
Preparing for the Storm
Authorities in several counties, including San Mateo, Santa Clara, and Solano, have already declared states of emergency in anticipation of the storm’s impact. Local governments have urged residents to remain indoors unless absolutely necessary and to avoid traveling in adverse weather conditions.
For those living in flood-prone areas, it’s a good idea to have emergency kits on hand with essentials like food, water, batteries, flashlights, and medications. Homeowners should also ensure that storm drains are clear and that gutters are properly maintained to prevent flooding. People in mountainous areas should stay informed of avalanche warnings and check the status of local roads before embarking on any travel.
Long-Term Impact and Climate Considerations
This atmospheric river is a reminder of the cyclical nature of California’s weather. While the state is known for its Mediterranean climate, marked by hot, dry summers and wet winters, extreme weather events like this have become more frequent and severe in recent years. With climate change affecting the region, experts predict that California will continue to see more intense rain events, which will have significant impacts on infrastructure, agriculture, and the daily lives of residents.
Although the atmospheric river will likely pass by the weekend, its effects will linger. Communities will need to assess the damage and begin the work of cleanup, particularly in areas impacted by flooding and landslides. Local officials are already working with emergency crews to ensure that critical services are restored quickly.
Conclusion
As Northern California faces the ongoing impacts of this powerful atmospheric river, residents are urged to stay prepared, stay safe, and heed the advice of local authorities. Whether through significant rain, snowmelt, avalanches, or power outages, the Pineapple Express system serves as a stark reminder of California’s vulnerability to extreme weather patterns. The full scope of its impact will unfold in the coming days, but the key takeaway is the importance of early preparation and safety in the face of unpredictable and potentially dangerous weather conditions.
