Waves of heavy rainfall in early December 2025 triggered landslides and flooding in parts of the Pacific Northwest. The flooding was the result of a powerful atmospheric river that hit the region around December 7th.
Atmospheric rivers are long, narrow bands of moisture that move like rivers across the sky, carrying water vapor from the tropics to the poles. They occur across the planet, most often in the fall and winter, with the West Coast of the United States typically affected by moist air originating in the Hawaiian Islands area. However, in this case, some of the moisture came from even more distant places, some 7,000 miles (11,000 kilometers) across the Pacific Ocean from near Philippines.
This map shows the total amount of precipitable water vapor in the atmosphere at 11:30 pm Pacific Time on December 10th. It is derived from NASA data. GEOS (Goddard Earth Observing System) and uses satellite data and physical models to approximate what is happening in the atmosphere.
Precipitated water vapor is the amount of water contained in a column of air, assuming that all the water vapor condenses into a liquid. Green areas of the map indicate the most moisture. Note that not all precipitated water vapor falls as rain; at least some remains in the atmosphere. There is also no limit to how much precipitation can fall, as the amount of precipitation can increase as more moisture enters the air column. However, it serves as a useful indicator of areas where excessive precipitation is likely to occur.
According to National Weather ServicePreliminary ground measurements showed that several locations in western Washington received more than 10 inches (250 millimeters) of rain in a 72-hour period ending the morning of Dec. 11. On December 10, Seattle-Tacoma International Airport set a daily rainfall record of 1.6 inches (40 millimeters).
On December 11, the river continued to flood. Skagit River And Snohomish River that day saw record or near-record flood levels. Floodwaters and landslides closed numerous roads, including eastbound lanes of I-90 out of Western Washington.
NASA Disaster Response Coordination System was activated to support the ongoing response efforts of the Washington State Emergency Operations Center. The team will make maps and information products publicly available. cartographic portal as new information becomes available.
NASA Earth Observatory images taken by Lauren Dauphine using GEOS data from NASA's GSFC Global Modeling and Assimilation Directorate. Story by Katherine Hansen.
- Cliff Mass Weather Blog (December 8, 2025) Stream has begun: Philippine connection. As of December 11, 2025
- National Aquatic Center, via X (December 10, 2025) Key messages about flooding in the Pacific Northwest. As of December 11, 2025
- National Weather Service (December 11, 2025) Miscellaneous hydrological data. As of December 11, 2025
- NOAA (February 21, 2025) What are atmospheric rivers? As of December 11, 2025
- USA today (2025, December 11) Catastrophic flooding prompts evacuation of Washington state residents. See the forecast. As of December 11, 2025
- Washington Post (2025, December 8) The 7,000 mile long atmospheric river stretches from the Philippines to the United States. As of December 11, 2025
