San Antonio woke up hazy, muggy and already working up a sweat on Thursday, June 18, 2026, with temperatures hovering near 80°F at local observation sites. The National Weather Service is warning that the real trouble arrives this afternoon, with highs near 99°F and heat index values expected to rocket well into the triple digits.
What To Expect This Afternoon
Skies will stay mostly sunny and hot through the afternoon, with south-southeast winds around 5 to 10 mph and gusts up to 20 mph pushing the daytime high close to 99°F. The NWS Austin/San Antonio has issued an Extreme Heat Warning from noon to 8 p.m., calling for "dangerously hot conditions with heat index values of 113-118 expected." In plain terms, it is the kind of afternoon where you should avoid extended outdoor activity from midday into the early evening and keep a close eye out for signs of heat illness.
Heat Safety And Cooling Centers
If you need a place to cool off, the city maintains a hub of cooling sites and heat resources at SA.gov/HotWeather, and you can also call 311 or the Community Connections Hotline at 210-207-1799 for locations. Local reporting notes the city may open extra cooling centers or extend hours when warnings are in effect, see the latest local guidance at the San Antonio Express-News. Stay hydrated, seek air conditioning when you can, and never leave children or pets in parked vehicles, even for a short time.
Friday Juneteenth Outlook
Friday, Juneteenth (June 19), should be a touch cooler but still sticky and uncomfortable, with highs near 94°F and a slight chance of afternoon showers or isolated thunderstorms after 1 p.m. Humidity will keep heat index readings elevated around 105 to 110°F in many neighborhoods, and southeast winds will stay on the breezy side at times. If you have outdoor holiday plans, try to shift the most active parts of the day to early morning or later in the evening and make sure there is shade and plenty of water.
Workers, event organizers and anyone spending long stretches outside should build in frequent rest and water breaks and keep tabs on vulnerable people, including older adults, very young children and anyone without reliable air conditioning. For the latest updates, follow NWS Austin/San Antonio and check the city's heat hub or call 311 before heading to a cooling center.
