KSAT Weather Alert: Severe Storms and Flash Flood Threat for San Antonio Tonight—Live Radar & Safety Tips

Updated 27 May 2025—San Antonio, Texas Early-Week Storm Recap Flashing lightning, booming thunder and pockets of golf-ball-size hail swept across San Antonio and the Hill Country late Monday, prompting the KSAT Weather Authority to issue multiple Severe Thunderstorm Warnings for Bexar, Kendall and Comal counties. KSAT Connect photos sent in by viewers showed vivid cloud-to-ground strikes over Loop 410 and sheets of hail carpeting lawns in Boerne. The National Weather Service logged wind gusts topping 60 mph at Stinson Municipal Airport, while radar estimates suggest localized rain totals of 1–2 inches—welcome moisture after an otherwise dry May. Why the Atmosphere Is So Unstable • A stalled frontal boundary draped over Central Texas keeps low-level moisture pinned in place. • Daytime highs near 90 °F combine with dew points in the mid-70s, pushing heat indices past 100 °F and adding fuel for late-day convection. • An upper-level disturbance sliding east from New Mexico acts as the spark, allowing towering cumulonimbus clouds to explode after sunset. KSAT Weather Forecast at a Glance Tuesday: Morning clouds, then sun heating the pavement to 92 °F. Isolated storms redevelop after 5 p.m.; any cell can drop quarter-size hail and 50 mph gusts. Wednesday–Thursday: A dome of high pressure noses in, driving temperatures to 101–103 °F—potentially the earliest triple-digit stretch on record for the Alamo City. A heat advisory is likely; limit outdoor work and hydrate often. Friday into the Weekend: The ridge weakens, restoring a 40 % chance of afternoon and evening thunderstorms. Highs retreat to the mid-90s but humidity remains oppressive. Safety and Preparation Tips • Park vehicles under cover to avoid hail damage. • Keep phones charged and enable Wireless Emergency Alerts plus the free KSAT Weather Authority App for real-time radar. • If thunder roars, head indoors: lightning can strike 10 miles from a storm core. • During the heat wave, check on elderly neighbors and never leave pets or children in cars—even with windows cracked. What This Means for Memorial Day Travelers Roadways will likely dry out by mid-morning, but residual ponding lingers on low-lying stretches of Loop 1604 and I-10. If you plan to float the Guadalupe or attend outdoor ceremonies, pack sunscreen, water and a portable rain jacket; pop-up storms may force brief delays, especially north of Highway 90. Looking Ahead: Early Hurricane Clues South Texas dew points already mimic mid-July, a reminder that hurricane season officially begins this Saturday, June 1. KSAT meteorologists urge residents to review evacuation routes, restock emergency kits and bookmark the KSAT Hurricane Tracker page before the first Gulf disturbance spins up. Stay Weather-Aware KSAT will continue to cut into programming with live warnings whenever storms threaten. For constant updates, follow @KSATWeather on X, join the KSAT Connect community to share your sky photos and tune to KSAT-12 on air or streaming for the latest San Antonio forecast.