Atmospheric rivers
“Atmospheric rivers are relatively long, narrow regions in the atmosphere – like rivers in the sky – that transport most of the water vapor outside of the tropics. While atmospheric rivers can vary greatly in size and strength, the average atmospheric river carries an amount of water vapor roughly equivalent to the average flow of water at the mouth of the Mississippi River. [...] When the atmospheric rivers make landfall, they often release this water vapor in the form of rain or snow.” (NOAA, 2025)
Sources
NOAA. 2025. “What are atmospheric rivers?” https://www.noaa.gov/stories/what-are-atmospheric-rivers.