Texas heat is just not letting up at night

The warmth wave in Texas has offered little reprieve. 

For 2 straight weeks, high temperatures in Del Rio have exceeded 100 degrees Fahrenheit every day — rising at its highest to 115 F. 

Just as worrisome — nighttime temperatures have set records and offered no relief. On all but sooner or later, Del Rio’s lowest temperature was at the very least 80 F, in accordance with National Weather Service data. 

Heat at night disrupts sleep and prevents the body from recovering and cooling down, making minimum temperatures a critical indicator of a heat wave’s severity, experts said. In lots of parts of the country, nights are warming faster than days — a sneaky risk to people’s health.

“There are quite a lot of studies on health impacts that show nighttime temperatures are particularly vital,” said Ben Zaitchik, a professor within the Earth and planetary sciences department at Johns Hopkins University who studies extreme heat. “The body’s collected heat stress can result in every kind of complications and the flexibility of the body to chill out at night will be critical.”

Texas State Climatologist John Nielsen-Gammon said temperatures during this heat wave within the state have threatened records at each ends of the spectrum — including maximums and minimums — in its urban centers.

“We have had a pair stations, mostly urban ones, which have come near having periods of time with record minimum temperatures — San Antonio and Houston,” he said.

Nielsen-Gammon said several areas, including Midland, San Angelo and Del Rio, have set records for weekly average temperatures, an indicator of the length and severity of this heat wave, which was triggered by a chronic stretch of high pressure.

Kristie Ebi, a professor on the Center for Health and the Global Environment on the University of Washington who makes a speciality of heat and climate change research, said deaths during heat waves typically start after the 24-hour mark as stress accumulates on the body.

“It takes some time for our heart to change into hot, before you see something like a heart attack,” she said. “Now we have behavioral mechanisms — it’s hot, we try to search out a spot to chill down. Now we have physiological mechanisms — sweating. There is a real effort to bring that core temperature down on the behavioral and physiological side.”

Ebi said the high nighttime temperatures and the prolonged nature of the Texas heat wave are particularly concerning. 

The toll of warmth is commonly underestimated partly because its cumulative stresses can exacerbate underlying health conditions. After a heat wave is complete, researchers will compare death data to prior years, control for other aspects after which tally the variety of “excess deaths” — individuals who wouldn’t have otherwise died if not for extreme temperatures. 

“A really small percentage of death certificates during a heat wave put down, ‘heat’ as an underlying cause,” Ebi, who studies heat deaths, adding that about half of excess deaths, on average, are from cardiovascular diseases. 

Climate change is causing temperatures to rise in Texas. Average day by day minimum temperatures have risen from 51.9 F in 1970 to 54.2 F in 2020 — a change of about 2.3 F, which is roughly in keeping with the general pace of warming within the state. 

“The whole lot’s been going up at in regards to the same rate — day by day minimums, day by day maximums, winter versus summer,” Nielsen-Gammon said. “We’re now 2 degrees above the twentieth century average in all seasons.”