As the western United States heads into its traditional dry season, water managers are assessing how winter rains have helped replenish the region’s reservoirs. The vast majority of precipitation that falls during the wet season results from atmospheric rivers (ARs) that rain down life-sustaining water but can also cause costly destruction. These fast-moving “rivers” of water vapor in the sky supply up to half of the region’s annual precipitation, with stronger ARs responsible for the majority of flood damages along the West Coast. To aid in predicting and monitoring these extreme weather events, NOAA Physical Sciences Laboratory (PSL) operates nine atmospheric river observatories at sites distributed along the coast from Washington to Southern California. These unmanned weather stations send round-the-clock observations back to the laboratory, which analyzes and displays the data publicly on its Atmospheric River Portal.