Preceded by more than a week of heavy rain, a slow-moving storm system dropped tremendous precipitation across much of Texas and Oklahoma during the nights of May 24–26, 2015, triggering record-breaking floods.

[5] Particularly hard hit were areas along the Blanco River in Hays County, Texas, where entire blocks of homes were leveled.

[7] According to Bob Henson from Wunderground, inflow of low-level moisture from the Gulf of Mexico and the combination of very slow moving large-scale storm systems set the stage for the floods.

He added,"Upper-level winds were largely aligned with the low-level frontal zone, an ideal setup for “thunderstorm training” (successive downpours over the same area).

In addition, rains were concentrated by several mesoscale convective vortices, small-scale centers of low-pressure that developed along the frontal bands, in some cases resembling mini-tropical cyclones.

[20] Entire blocks of homes in Wimberley were swept away by a "tidal wave of water"[2] with officials reporting 350–400 residences destroyed in the town alone.

[20] On May 23, flash flooding along Highway 20 near Claremore claimed the life of a firefighter attempting to rescue people in an apartment complex.

[28][29] On May 26, President Barack Obama announced federal resources to help affected areas in Texas, and signed a disaster declaration for Oklahoma.

[32] A study by Utah State University [33] analyzed the pathway in which anthropogenic global warming contributed to the persistent precipitation in May 2015: Warming in the tropical Pacific acted to strengthen the teleconnection toward North America, modification of zonal wave-5 circulation that deepened the stationary trough west of Texas, and enhanced Great Plains low-level southerlies increasing moisture supply from the Gulf of Mexico.

[34] The report Regional Climate Trends and Scenarios for the U.S. National Climate Assessment (NCA) from 2013 by NOAA, projects that parts of Texas, and parts of the Great Plains region can expect up to 30% (High emissions scenario based on CMIP3 and NARCCAP models) increase in extreme precipitation days by midcentury.

[35] A study from April 2015 concluded that about 18% of the moderate daily precipitation extremes over land are attributable to observed temperature increase since the Industrial Revolution and that this primarily results from human influence.