San Antonio’s September heat has been unusually persistent at night as well as during the day. Through September 17, the city had recorded 110 straight days with a minimum temperature of at least 70 degrees, according to the San Antonio Express-News. The streak surpassed the previous city record of 106 days, set in 2016. The pattern follows an exceptionally hot August: according to the National Weather Service Austin/San Antonio, August 2026 was San Antonio’s sixth-warmest August on record.
The numbers behind the record pace
The Express-News reported that San Antonio’s average low through September 15 was 78.6 degrees, the warmest start to a September for overnight temperatures in the city’s records. Through Thursday, the average high was 98.4 degrees and the average low was 78.4 degrees, leaving the month’s combined average temperature at 88.4 degrees through September 17.
The combined average was approaching San Antonio’s September record of 87 degrees, set in 2023 for the month as a whole. The Express-News reported that a substantially cooler remainder of September would be needed to prevent a new record, while the available outlook made that outcome appear unlikely.
Little relief in the near-term outlook
The forecast described by the Express-News called for Friday temperatures in the mid- to upper 70s during the morning, near 90 degrees by noon and about 97 degrees in the afternoon. The heat index could reach 103 degrees, while the chance of rain in San Antonio was about 10 percent.
Weekend rain chances were also expected to remain low, with afternoon temperatures in the upper 90s and Sunday’s high forecast at about 97 to 98 degrees. A weak front was expected to stall in northern Texas, bringing better rain chances to North Texas than to San Antonio. The city’s chance of rain along the front was put at roughly 20 percent, and high temperatures were expected to remain in the mid- to upper 90s for at least the following 10 days, with morning lows in the mid- to upper 70s.
Broader strain during extreme heat
High temperatures can also increase electricity demand across Texas. The U.S. Energy Information Administration reported that the Electric Reliability Council of Texas reached an hourly peak load of about 91.1 gigawatts, or approximately 91,308 megawatts, on July 22, 2026, during a heat wave: EIA. That statewide figure provides context for heat-related demand but does not by itself establish a local San Antonio grid impact.
Practical precautions
Who faces the greatest heat risk?
Bexar County says adults 65 and older, children 4 and younger, people with certain medical conditions and those without access to air conditioning face higher risks when temperatures and heat indexes are high. The county’s guidance provides a local framework for assessing who may need help during a prolonged stretch of hot days and warm nights: Bexar County. The same county guidance warns that a car’s interior can reach 102 degrees in 10 minutes and 120 degrees or more in 30 minutes on an average 85-degree day, underscoring why children and pets should never be left in parked vehicles.
With afternoon temperatures expected to stay near the upper 90s and overnight cooling limited, residents should use air-conditioned spaces when needed and review applicable utility-service policies. Children and pets should not be left in parked vehicles, even for a short time.
