Heavy rains trigger flash floods, close roads in San Antonio

Torrential rains struck San Antonio, Texas, on the morning of May 30, 2025, unleashing flash floods that closed roads and snarled traffic across Bexar County. The lower levels of Interstate 35 under San Pedro Avenue were hit hardest, with vehicles stranded in rapidly rising waters. The Bexar County HALT system flagged 16 locations with hazardous water levels, including Alamo Heights and Old O’Conner Road. Police diverted traffic to upper highway levels as drivers navigated treacherous conditions. The storms, sweeping through the city, prompted warnings to avoid flooded areas and prioritize safety.

Local authorities ramped up efforts to monitor road conditions. The HALT system, designed to detect high water, played a critical role in identifying at-risk areas. The situation underscores the region’s vulnerability to flash floods, a recurring issue during heavy rain events.

The storms’ impact spread across urban and rural areas of Bexar County. Drivers reported challenges on secondary roads, while major highways faced significant delays. Key affected areas include:

• Interstate 35 lower levels at San Pedro Avenue.
• Old O’Conner Road, where a stalled vehicle was reported.
• HALT-monitored sites like Alamo Heights and Schertz.

Real-time monitoring

The High-Water Alert Lifesaving Technology (HALT) system uses sensors to track rising water at critical points. On May 30, 16 locations triggered red alerts, signaling road closures. Deployed across 150 sites in Bexar County, the system employs flashing lights or light-and-gate combinations to warn drivers.

HALT data is updated live on BexarFlood.org, helping drivers plan alternate routes. The system, maintained through a partnership between Bexar County, the City of San Antonio, and the San Antonio River Authority, allows residents to sign up for closure alerts via email or text.

Continuous monitoring is vital in a flood-prone region. San Antonio’s shallow soils and high rainfall rates heighten the risk of rapid inundation.

Hardest-hit areas

The storms flooded both urban and rural zones. Downtown, the lower levels of Interstate 35 accumulated water quickly, a known issue during heavy rains. Stranded vehicles required police intervention to reroute traffic.

Beyond the city center, roads like Old O’Conner Road faced similar challenges. A stalled car was reported there, highlighting the dangers of driving through flooded areas. Other sites, including Alamo Heights, Cave Lane, and Stahl, also logged dangerous water levels per HALT data.

Affected locations include:

• Comanche Cross and Contour Drive, with sensors signaling risks.
• Fort Sam Master Sts and Leslie, in residential areas.
• Pinn Road and Rodriguez, with traffic halted.

Authorities’ response

San Antonio police swiftly closed the lower levels of Interstate 35 and redirected traffic. Emergency crews monitored other roads, while barriers were set up at critical points. The city’s Public Works Department, led by Razi Hosseini, stressed the importance of heeding signs and barricades.

Bexar County Public Works deployed round-the-clock teams to address flooding reports. Residents were urged to check city websites for updates and steer clear of flooded zones.

The rains demanded coordination across agencies. The San Antonio River Authority, a partner in flood control efforts, provided data on river and creek conditions.

History of flooding

San Antonio and Bexar County are no strangers to flooding, given their location in the so-called Flash Flood Alley. The region’s mix of heavy rains and impermeable soils triggers rapid inundation. Past events, like the floods of 1998 and 2013, left lasting impacts on local infrastructure.

Since 2007, Bexar County’s flood control program has invested $500 million in 50 projects to mitigate damage. The initiative, backed by the city and the San Antonio River Authority, emphasizes regional strategies to curb flooding.

Key projects include:

• Building drainage channels in urban areas.
• Upgrading runoff systems on highways.
• Installing HALT sensors at low-water crossings.

Driver guidance

Authorities reinforced the “Turn Around, Don’t Drown” campaign to warn drivers about the risks of flooded roads. National Weather Service data shows most flood-related deaths occur in vehicles.

Drivers were advised to avoid high-risk areas, especially at night when visibility is low. Police noted that ignoring barricades can lead to fines of up to $2,000 or 180 days in jail. Rescues from flooded areas may cost $650 per vehicle occupant.

Safety tips include:

• Checking BexarFlood.org before traveling.
• Avoiding roads with standing water.
• Planning alternate routes on rainy days.

Weather conditions

The National Weather Service issued flash flood warnings for San Antonio and nearby areas on May 30 morning. Radars tracked a line of thunderstorms moving through, with heavy rainfall concentrated south of the city.

The storms posed risks of flooding in creeks, streams, and urban areas. Forecasts indicated rain would persist through the day, requiring ongoing vigilance.

High humidity and a cold front fueled the adverse conditions. Areas east of Interstate 35 saw the heaviest rainfall accumulations.

Traffic disruptions

The Interstate 35 closure caused major backups in downtown San Antonio. Drivers were rerouted to upper levels, but heavy traffic led to delays. Secondary roads, like North Loop and Weidner Road, also faced interruptions.

Reports of stranded vehicles underscored the situation’s severity. On Old O’Conner Road, drivers struggled to navigate flooded sections. Police urged avoiding non-essential travel during the storms.

Disruptions included:

• Delays on urban and rural routes.
• Closures at HALT-monitored sites.
• Detours in central areas.

Prevention and infrastructure

Bexar County’s flood control program continues to expand its infrastructure. Beyond HALT, the region invests in drainage channels and alert systems. The San Antonio River Authority monitors rivers and creeks to anticipate risks.

The city also reviews development plans to minimize runoff impacts from new construction. Residential and commercial projects undergo strict evaluations to ensure drainage compatibility.

Prevention efforts include:

• Regular maintenance of culverts and drains.
• Educational campaigns for drivers.
• Updated flood risk maps.

Current situation

By late morning on May 30, rains began to ease in parts of San Antonio, but flood warnings remained active. HALT continued to monitor 16 critical sites, with potential for additional closures.

Drivers were urged to stay cautious, particularly in low-lying areas. Police and emergency crews stayed on alert for further reports. The San Antonio River Authority updated river data, noting risks near Leon Creek.