When intense storms bring days of heavy precipitation, flooding, and power outages, an atmospheric river can be the driving force behind them. Recent events across the western United States show how quickly these systems can escalate from steady rainfall into widespread disruption.
Atmospheric rivers are one of several weather patterns that trigger weather watches and warnings. In December 2025, a series of atmospheric rivers went through Washington and Oregon before shifting south, spreading a flood threat into northern California just days later. Understanding these systems helps homeowners better prepare for dangerous weather before conditions worsen.
- What Is An Atmospheric River?
- What Causes An Atmospheric River?
- The Impact Of Atmospheric Rivers On Communities
Track changing weather conditions with the Tempest Weather System, a personal weather station built for hyperlocal accuracy.
What Is An Atmospheric River?
An atmospheric river is a long, narrow corridor of concentrated moisture that moves through the atmosphere, transporting vast amounts of water vapor from warmer regions toward cooler land areas. When these systems make landfall, that moisture often falls as prolonged rain or heavy mountain snow.
What are atmospheric rivers best known for? Their ability to deliver extreme precipitation over short periods. A common example is the Pineapple Express, an atmospheric river that pulls warm, moisture-rich air from near Hawaii toward the U.S. West Coast. These systems are often responsible for multi-day rain events that overwhelm rivers and drainage systems. While not all of them pose a safety risk, they are still important to monitor.
Learn how rainfall intensity varies by region in our How Much Rain Is A Lot Of Rain In Different U.S. Regions? blog.
What Causes An Atmospheric River?
If you are asking what causes an atmospheric river, the answer lies in the interaction between warm ocean air, strong winds, and large-scale pressure patterns. Moist air forms over the Pacific Ocean, then powerful winds concentrate it into a narrow band that can stretch thousands of miles.
During the December 2025 event, multiple Pacific storms reinforced one another, creating a procession of atmospheric rivers that repeatedly hit the same areas. This stacking effect increased rainfall totals and raised flood risk as rivers and soil had little time to recover between storms.
Professionals can do multi-hazard monitoring by running a weather risk assessment.
The Impact Of Atmospheric Rivers On Communities
Atmospheric rivers can deliver critical water supplies, but their impacts can also be severe. In western Washington, recent storms dumped several inches of rain in just a few days, following an earlier stretch that delivered over a foot of precipitation in some areas. The result was record flooding and levee breaches along rivers near populated areas.
Beyond flooding, these systems can trigger landslides, damage infrastructure, and cause dangerous windstorms. During the same weather pattern, wind gusts exceeding 70 mph caused widespread power outages and property damage across the Northwest. Accurate forecasting and early awareness help reduce risks to lives, homes, and local economies.
Learn practical safety steps on how to prepare for severe weather.
Get Accurate Hyperlocal Weather Forecasts With The Tempest Weather System
Understanding what an atmospheric river is matters most when it connects to real conditions where you live. Broad forecasts often describe regional threats, but impacts can vary dramatically from one neighborhood to the next, especially during prolonged storm sequences.
The Tempest Weather System delivers real-time, hyperlocal weather data from your exact location. During atmospheric river events, this visibility helps homeowners track rainfall totals, wind gusts, and pressure changes as conditions evolve. With clearer insight into what is happening outside your door, it becomes easier to make informed decisions when severe weather threatens.
Shop the Tempest Weather System to stay prepared before the next atmospheric river makes landfall.