'Not normal': Austin breaks heat index record; blazing heat to linger with no end in sight

Austin broke a record Wednesday for its highest heat index value, blazing in at 118 degrees at Camp Mabry, according to the National Weather Service.

Although heat index values, or the "feels like temperature," are not an "official" record, National Weather Service meteorologist Mack Morris said this is the highest value ever detected in Austin. The previous high heat index value was 116 degrees in August 2016.

"This is not normal for June," Morris said. "It does get hot, but this kind of humidity is not normal."

More:Officials urge residents to keep cool amid Austin heat wave. Here's what they propose.

Weekend forecast: Hot

Heading into the weekend, temperatures are expected to stay hot. And though it will be slightly cooler than earlier this week, Central Texas, including Austin, will be under a heat advisory Friday. Meteorologists said the heat index could reach 112 degrees in Austin.

The weather service predicts these heat advisories and possibly additional excessive heat warnings will continue to be issued through the weekend, into next week and possibly longer with "no clear end in sight."

Explainer:Austin's weather is blistering this summer, excessive heat explained in four charts

Throughout the first half of the week, Austin and much of Central Texas were under an excessive heat warning as temperatures hovered around 104 and heat indexes reached near 115.

On Saturday and Sunday, temperatures are expected to reach about 103, with heat indexes climbing to 112, at Camp Mabry, according to weather service forecasts.

Any rain in Austin's forecast?

While recent rain — which at Austin-Bergstrom International Airport totaled nearly 1 inch Wednesday — might have seemed like a reprieve from scorching temperatures, it could push heat indexes higher.

More rain means more water in the ground, which equals more humidity and, therefore, higher heat indexes. Morris said the humidity has been the driving force behind making this heat wave feel worse than previous ones. So, the recent rain could cause heat indexes to continue staying high as this heat wave continues.

"We're getting these extreme heat indexes due in part to our fairly wet spring and recent rain," Morris said. "Last summer was hot, but it was more of a dry heat. We didn't have as much rain in the spring. So wasn't as bad. This summer has been way worse already."

How are the water supplies?

Readings from the Lower Colorado River Authority show Travis and Buchanan reservoir lakes have a combined total of 1,026,403 acre-feet as of Thursday. The LCRA considers them full when both combined are at 2 million acre-feet.

Lake Travis is about 45% full at about 638 feet above mean sea level. That's 31 feet below the June average. Lake Buchanan is 63% full at about 1,002 feet above mean sea level, which is just slightly below its June average by about 11 feet.

Take precautions as dangerous heat persists

Local officials urged residents on Wednesday to take proper precautions before heading outdoors by drinking plenty of water, staying out of the sun if possible, taking breaks and watching for signs of heat-related illnesses.

Morris said this type of high-humidity heat is exceptionally dangerous because the body's cooling system can't work as well because sweat doesn't evaporate as easily.

Heat claimed more lives in the U.S. than any other weather-related event in 2022 with 148 deaths, according to the National Weather Service. That's nothing new, though, as heat has been the No. 1 cause of weather fatalities for 30 years, with an average of 164 deaths a year.

"With this heat, in this humidity, it's dangerous, and we need to pay attention to that," Mayor Kirk Watson said during the news conference Wednesday.

Climate change influencing high heat

Morris said heat waves are only going to increase as the planet warms due to climate change.

Climate Central, a nonprofit science organization, said climate change played an "exceptional" role in this week's scorching temperatures. The group's Climate Shift Index map, which provides daily measures of how climate change is affecting air temperatures, showed that climate change made this week's excessive heat warnings in Central Texas five times more likely to occur.

"People can say all they want about climate change. But the planet's definitely warming, and we're the cause of it," Morris said.