San Antonio starts Monday, August 10, 2026, near 79 degrees under mostly clear skies, but the relief will be short-lived. Temperatures are expected to climb to about 97 degrees, with the heat index reaching 106. A brief storm chance arrives late in the afternoon, offering only a slim interruption to another steamy South Texas day.
The National Weather Service forecasts mostly sunny conditions through the morning, followed by a 20% chance of showers and thunderstorms after 4 p.m. South-southeast winds will run 5 to 10 mph, and any storm activity should be scattered rather than widespread.
Heat Builds Through Midweek
Tuesday looks hotter and drier, with a high near 99 degrees and a heat index as high as 107. Wednesday and Thursday could reach 100 degrees, while Friday is expected to top out near 99 before the weekend settles into mostly sunny, upper-90s weather.
Overnight temperatures will offer limited relief, dipping only to around 77 or 78 degrees. Winds will generally blow from the south or southeast, with occasional nighttime gusts reaching 20 to 30 mph later in the week.
Small Storm Window Monday Evening
The best chance for rain is Monday afternoon into early evening, when a few showers or thunderstorms may develop near the I-35 corridor and areas east of the city. The chance drops to nearly zero Tuesday and remains minimal through the weekend, so most outdoor plans should stay dry—but very hot.
Heat Safety Matters
The City of San Antonio recommends drinking water, taking breaks in shade or air conditioning, and avoiding strenuous activity during the hottest part of the day, generally from 2 to 7 p.m. Older adults, young children, people with medical conditions and anyone without reliable air conditioning face higher risks from prolonged heat.
No heat advisory or other weather alert is listed for San Antonio on Monday morning. Still, with triple-digit heat-index readings possible and the hottest stretch arriving midweek, residents should treat the forecast seriously and never leave children or pets in a parked vehicle.
