Spring rains have saturated the ground like a soggy sponge and primed Austin for dangerously high heat index levels, according to the National Weather Service.
The “feels like” temperature on Thursday afternoon hit 118 degrees at Camp Mabry in West Austin, National Weather Service data shows, tying the all-time record.
The threat of a high heat index prompted forecasters to issue their first extreme heat warning since last summer, and their first heat index related warning since 2024.
“We don’t see these every day,” said Matthew Brady, lead meteorologist at the NWS Austin/San Antonio office. “People need to be aware of the symptoms of heat exhaustion or heat stroke when working outside and being outside.”
The heat index is different from air temperature because it factors in how humidity increases people’s experience of heat.
That “feels like” temperature is often worse in Austin in the spring or early summer when humidity from heavy rains meets the onset of high summer temperatures.
The sudden swelter after cooler spring weather can be especially dangerous because people’s bodies are not yet acclimatized to extreme heat, almost like trying to run a marathon with no training.
“Temperatures this hot in August, we’ve already felt that probably five or six times by that point,” said Mary Wasson, a meteorologist for the Austin American-Statesman. “But early in the season, it’s definitely when you want to take those big extra precautions.”
Experts say it is one reason emergency room visits for heat-related illness often are higher early in the summer.
The National Weather Service issues extreme heat warnings when air temperatures are expected to reach 102 or higher, or when the heat index is forecast to reach 110 degrees for two or more hours.
Austin’s highest ever heat index was recorded at Camp Mabry in June of 2023, when it reached 118 degrees.
Forecasters with the National Weather Service believe Austin may threaten a different record this time around: the warmest low temperature for June 19.
They say the lowest it may get on Friday is 80 degrees, which would tie the current record of 80 degrees also set during that June 2023 heat wave.
The NWS is urging people to stay hydrated and take frequent breaks if working or taking part in recreation outside.
“If you’re still outside and you start not to sweat, then that could be one of those symptoms towards a heat stroke,” Brady said. “So you want to be very careful.”