Early April 2025 saw torrential rains battering down across the South and Midwest USA just after a slew of storms in March. A Category 5 atmospheric river was behind the destructive floods and wind, which resulted in deaths across seven states – Tennessee, Kentucky, Missouri, Arkansas, Georgia, Indiana and Mississippi. Preliminary estimates place insured losses from flooding and severe weather in early April 2025 between $1 billion and $3 billion, encompassing both private insurers and federal insurance schemes (Reinsurance News, 2025).
A week-long unrelenting rainfall that plagued the central and southern US was fuelled by a powerful meteorological phenomenon: a Category 5 atmospheric river (CNN, 2025a). Atmospheric rivers are long and narrow corridors of concentrated moisture in the atmosphere that extend between 250 and 375 miles. These “rivers in the sky” can transport moisture volumes equivalent to 25 Mississippi Rivers, channelling vast amounts of water from the tropics to polar regions (NASA, 2018). The Center for Western Weather and Water Extremes reports that this Category 5 atmospheric river was one of many that swept through the South, Midwest and Appalachians between 1 and 7 April, which provided significant moisture that caused intense rainfall (CW3E, 2025).
While atmospheric rivers are widely recognised as key drivers of precipitation in the western US, their influence in the central and eastern US is often overlooked. In fact, atmospheric rivers occur more frequently along the eastern coast, but the amount of rain they bring often pales in comparison to rain from afternoon storms, cold fronts and hurricanes that are common in the east (CNN, 2023). Under the right conditions, however, Eastern atmospheric rivers can pose a substantial hazard.
The dynamics of atmospheric rivers differ significantly by region. In the west, these systems derive moisture from the cooler Pacific Ocean, where the atmospheric system builds and reaches its peak strength before reaching the western coast. The moisture is then released as the air masses ascend the region’s extensive mountain ranges (CNN, 2025a). In contrast, eastern atmospheric rivers form over the warmer Gulf of Mexico, carrying more moisture and peaking in strength after making landfall (Algarra et al., 2020). Without substantial topography in the east, atmospheric rivers can travel far inland before meeting a front to form rain (CNN, 2025a).
In the case of this Category 5 atmospheric river, the stream of moist air collided with a stationary front that lingered above Arkansas through Kentucky, forcing storms to form. Such fronts are rarely stationary for extended periods, making the intensity of this atmospheric river an exceptional case (CNN, 2025a).
The deluge triggered by this atmospheric river inundated communities from Texas to Ohio. These areas had already been saturated by severe storms with hail and rain just days earlier, giving communities no room to recover (NYT, 2025a; CNN, 2025c). Rushing waters, violent winds and compromised infrastructure from this event alone have killed at least 24 people across seven states (CBS, 2025).
Kentucky bore the brunt of the flooding. On 7 April, the Kentucky River crested at 49 feet—nearly overtopping the flood wall system in the state capital of Frankfort (CBS, 2025). Further west, the Ohio River near Louisville crested at 37 feet on 9 April, placing it among the top 10 peak river levels ever recorded (NWPS, 2025). The rising water disrupted essential services, including the water supply in parts of Frankfort and Harrodsburg, where floodwater from the swollen Kentucky River threatened the water pump infrastructure (CNN, 2025b). Evacuation orders were issued for small towns of Butler and Falmouth along the Licking River, low-lying communities along the Kentucky River, and the and the city of Shelbyville, Indiana, situated along the Big Blue and Little Blue Rivers (NYT 2025b).
With climate change raising atmospheric temperatures, we can expect wetter atmospheric river events as warm air can contain more water (CNN, 2023; Payne et al., 2023). A NASA-led study suggests that the number of atmospheric rivers will be fewer, but each will spread 25% longer and wider, which increases the frequency of extreme weather conditions by around 50% globally (NASA, 2018).
This report is accompanied by a flood footprint for the event, detailing extents and depths of the flooding in areas affected in the South and Midwest USA. Download it via our Client Portal or request a copy by emailing eventresponse@jbarisk.com.
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Algarra, I. et al., 2020. Significant increase of global anomalous moisture uptake feeding landfalling atmospheric rivers., Nature Communications, 11(1). doi:10.1038/s41467-020-18876-w.
CBS, 2025. Relentless rain and storms kill at least 24 in South and part of Midwest. [Online]. Available from: https://www.cbsnews.com/news/rain-storms-20-dead-south-midwest-sever-weather/ [Accessed 21 April 2025]
Center for Western Weather and Water Extremes (CW3E), 2025. CW3E Event Summary: 1-7 April 2025 East Coast ARs. [Online]. Available from: https://cw3e.ucsd.edu/cw3e-event-summary-1-7-april-2025-east-coast-ars/ [Accessed 21 April 2025]
CNN, 2023. What is an atmospheric river? [Online]. Available from: https://edition.cnn.com/2023/03/09/weather/what-is-an-atmospheric-river-xpn/index.html [Accessed 21 April 2025]
CNN, 2025a. This notorious West Coast phenomenon fueled historic floods in the East. Another one is on the way. [Online]. Available from: https://edition.cnn.com/2025/04/18/weather/kentucky-floods-atmospheric-river-climate/index.html [Accessed 21 April 2025]
CNN, 2025b. Flood-weary residents face rising rivers despite rain finally stopping in central and southern US. [Online]. Available from: https://edition.cnn.com/2025/04/07/weather/rain-flood-south-midwest-storms-hnk/index.html [Accessed 21 April 2025]
CCN, 2025c. The reason for an outburst of deadly storms early in the year could be lurking in the ocean. [Online]. Available from: https://edition.cnn.com/2025/04/12/weather/why-storms-have-been-so-bad/index.html [Accessed 21 April 2025]
NASA, 2018. Climate change may lead to bigger atmospheric rivers. [Online]. Available from: https://science.nasa.gov/earth/climate-change/climate-change-may-lead-to-bigger-atmospheric-rivers/ [Accessed 21 April 2025]
National Water Prediction Service (NWPS), 2025. Ohio River at Alpine Upper. [Online]. Available from: https://water.noaa.gov/gauges/mluk2 [Accessed 21 April 2025]
New York Times (NYT), 2025a. 1 Dead as Severe Storms Erupt Across a Vast Stretch of the U.S. [Online]. Available from: https://www.nytimes.com/2025/03/30/weather/tornado-storms-missouri-illinois.html [Accessed 21 April 2025]
New York Times (NYT), 2025b. Rivers in Central U.S. Swell Rapidly as Storm Inundates Region. [Online]. Available from: https://www.nytimes.com/2025/04/05/weather/severe-storm-flood-central-us.html [Accessed 21 April 2025]
Payne et al., 2020. Responses and impacts of atmospheric rivers to climate change. Nature reviews Earth & Environment, 1(3). Pp143-157. doi:10.1038/s43017-020-0030-5.
Reinsurance News, 2025. April US floods & SCS outbreak to cause insured losses up to $3bn: Gallagher Re. [Online]. Available from https://www.reinsurancene.ws/april-us-floods-scs-outbreak-to-cause-insured-losses-up-to-3bn-gallagher-re/ [Accessed 21 April 2025]
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