San Antonio and South-Central Texas are bracing for a severe flash flooding threat starting Wednesday evening. An incoming Pacific cold front will interact with lingering tropical moisture from dissipated Hurricane Polo. The National Weather Service reports this system will deliver widespread rainfall totals of 2 to 4 inches, with isolated areas receiving up to 8 inches through Saturday along the Interstate 35 corridor.
A flood watch takes effect for San Antonio at 7 p.m. Wednesday. Wednesday begins mostly dry and hot with high temperatures reaching the mid-90s and heat index values peaking near 104 degrees. Atmospheric conditions will rapidly deteriorate overnight as thunderstorms push through the Edwards Plateau and the Hill Country.
Timeline of the Storm and Flood Threat
Forecasters expect the heaviest rainfall and highest flash flood risks to materialize on Thursday as the cold front stalls or moves closer to the I-35 corridor.
- Wednesday: Mostly dry and humid daytime conditions feature morning temperatures in the mid-70s and afternoon highs reaching 93 to 95 degrees. Isolated storms are possible before the 7 p.m. flood watch activation.
- Thursday Morning: Storm chances rise sharply. There is a 40% chance of rain between 4 a.m. and 8 a.m., jumping to 60% by mid-morning across the San Antonio metro area.
- Thursday Midday: The peak threat window spans from 10 a.m. to 3 p.m. with an 80% chance of rain. Intense downpours could produce rainfall rates exceeding 2 to 3 inches per hour, creating dangerous flash flooding on roads and low-water crossings. Strong, isolated storms may also generate wind gusts up to 60 mph, small hail, and an isolated tornado.
- Thursday Night and Friday: Continued storm chances depend on the precise movement of the cold front. Friday morning commuters should watch for flooded city streets and highways as lingering showers persist, though overall rain chances will taper off to 30% to 40% by Friday afternoon.
Temperature Relief and Drought Context
The incoming cold front will provide a substantial break from the high-90s and triple-digit heat that has dominated South-Central Texas. High temperatures will drop into the upper 80s on Thursday, sliding further into the low 80s for Friday, Saturday, and Sunday. Weekend morning lows are expected to settle into the upper 60s.
While the heavy rainfall carries a flash flood risk, local officials note the precipitation will provide beneficial moisture to Bexar County. Recent reports from the U.S. Drought Monitor indicate the county has slipped back into moderate drought conditions, with active outdoor burning bans in place.
Safety Guidelines for Motorists
Meteorologists and emergency management officials urge residents to take the flood watch seriously and avoid unnecessary travel, particularly at night. Drivers are reminded of the standard safety mantra: “Turn around, don’t drown.” Just a foot of fast-moving water can sweep a vehicle away, and low-water crossings across San Antonio and the surrounding “flash flood alley” can become impassable in minutes.
