RIO GRANDE VALLEY, Texas – It was a sight for sore eyes in San Antonio as much-needed rainfall swept through the region on Wednesday and Thursday. However, the heaviest downpours fell just south of the Alamo City, triggering severe flooding across South Texas.
A collection of daily blog posts from the KSAT Weather Authority.
School districts and colleges across the region announced class cancellations on Friday due to the dangerous weather. The Texas Department of Transportation shared footage of stranded vehicles throughout Hidalgo County, with flooding affecting cities like Donna, Weslaco, Pharr, San Juan, and McAllen.
The storm created treacherous conditions, with rescue crews responding to multiple flash flood emergencies, particularly Thursday afternoon. In the rarest of circumstances, these flash flood emergencies were issued to warn residents of rapidly rising waters.
What caused the storm?
The heavy rains were triggered by a low-pressure system that formed in the Pacific Ocean, pushing moisture over the mountains of Mexico. As a slow-moving upper trough settled over northeastern Mexico, it continued to rely on the moisture in the gulf. All of that moisture was allowed to just sit over South Texas. These atmospheric conditions created an environment ripe for widespread showers and thunderstorms.
.@NOAA's #GOESEast 🛰️ is tracking the nation's weather this morning with enhanced color imagery showing different temperature/moisture characteristics of air masses. #GOES16#Thunderstorms and heavy rain are continuing to bring a flooding threat to southern Texas and parts of… pic.twitter.com/4NZlVW7O65
— NOAA Satellites (@NOAASatellites) March 28, 2025
The ongoing drought in Deep South Texas and the Rio Grande Valley, combined with dry soils, amplified the flash flood risks, as the ground struggled to absorb the moisture.
Records Shattered by the Storm
In less than two days, the area received half of its average annual rainfall, leading officials to issue warnings and close schools in anticipation of more rain on Friday.
The storm’s rainfall set new records across the region. McAllen recorded 4.96 inches of rain, breaking its previous record set in 1999. But it was Brownsville that saw the most impressive totals, with 5.3 inches of rain falling Thursday, surpassing a record that had stood since 1911. Meanwhile, Harlingen experienced 3.72 inches of rain, breaking its 102-year-old record set in 1923.
According to the National Weather Service, 4.35 inches of rain fell in McAllen between 1 p.m. and 4 p.m. On the coast, areas like Port Isabel, Laguna Heights, and Laguna Vista saw as much as 7 inches of rain before 7 a.m. Thursday.
When will it end?
Though the heavy rains are expected to ease by the weekend, more moisture is still anticipated to fall as the slow-moving upper trough continues to push tropical moisture northward from Mexico. While the worst may be over, the lingering effects of the storm will be felt for days to come.
- Read more from the meteorologists on the Whatever the Weather page
- Download KSAT’s weather app for customized, accurate forecasts in San Antonio, South Texas or wherever you are
- Find the latest forecasts, radar and alerts on the KSAT Weather Authority page
