Rivers in the sky are raining down on the Pacific Northwest. What are they?

Atmospheric rivers are large bands of water vapor in the sky. They are dumping trillions of gallons of water on Washington and Oregon, just as high tides and winds batter shorelines.

<img src='https://npr.brightspotcdn.com/dims3/default/strip/false/crop/3829x2553+0+0/resize/3829x2553!/quality/85/format/webp/?url=http%3A%2F%2Fnpr-brightspot.s3.amazonaws.com%2F3b%2F6f%2F2ddc4c6345e4ab2246d52e61647e%2Fgettyimages-1829280584.jpg' alt='STANWOOD, WASHINGTON - DECEMBER 6: In an aerial view, floodwaters surround a home on December 6, 2023 in Stanwood, Washington. Atmospheric river conditions in the region brought heavy rains and flooding.'/><p>Atmospheric rivers are large bands of water vapor in the sky. They are dumping trillions of gallons of water on Washington and Oregon, just as high tides and winds batter shorelines.</p><p>(Image credit: David Ryder)</p><img src='https://media.npr.org/include/images/tracking/npr-rss-pixel.png?story=nx-s1-6032777' />