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San Antonio had 17 days of triple-digit heat in June. The norm is two.

Numerous Texas cities observed a siege of 100-degree days in June amid extreme drought

Forecast highs on the Fourth of July in Texas from the European model. (WeatherBell)
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Blazing hot and bone-dry Texas is in the midst of a vicious, reinforcing climate cycle. It keeps getting drier as relentless heat saps moisture from the ground. And it keeps getting hotter as the parched soil loses moisture that would help hold the heat in check.

The outcome of this feedback loop — which began in May — is a record onslaught of 100-degree days in population centers across the state.

San Antonio — the site of the lethal heat-related migrant tragedy earlier this week — has seen high temperatures of at least 100 degrees on a record 17 days this month; in an average June, it sees just two.

Amid the heat, power demand in Texas soared to an all-time high last week, Reuters reported. But, so far, the Electric Reliability Council of Texas, which operates the state’s grid, has met demand aided by new wind and solar power plants the news agency wrote.

Gulf system to bring some heavy rain to coastal Texas

Although the heat has eased modestly to close out June, a surge of even more severe heat is on the way. With little to disrupt this unforgiving weather pattern, the tally of dangerously hot days — intensified by human-caused climate change — is set to continue its rapid rise.

The heat by the numbers

San Antonio has already seen more than a full summer’s worth of 100-degree days. The city has registered 22 such days, 17 in June and 5 in May, the most on record year-to-date by far; 2009, the previous record holder, only had 13 up to this point. The average yearly 100-degree day count in San Antonio is 18, the great majority of which typically occur in July and August.

Amid the torrent of these June triple-digit days, San Antonio set eight record highs, soaring to a maximum of 105 on June 12. The city also set eight record highs in May, and two in April.

While near the epicenter of this freakish early heat, San Antonio is not alone. Numerous other Texas cities have endured a historic number of 100-degree days this June, including:

  • Del Rio: 23 days, most on record tied with 2018 and 1953
  • Austin: 21 days, most on record topping 20 in 2008
  • Abilene: 20 days, second-most behind 21 in 1953
  • Waco: 16 days, second-most on record behind 17 in 2011 and 1998
  • Victoria: 11 days, most on record topping 8 in 2009
  • Dallas-Fort Worth: 9 days, fourth-most on record
  • Houston: 5 days, fifth-most on record

Unsurprisingly, many of these cities are on track to observe their hottest June on record, including San Antonio, Houston and Austin.

Cities seeing their hottest June on record also stretch east along the Gulf Coast and into parts of the South. Cities including New Orleans, Mobile, Ala., and Pensacola, Fla., are all vying for a top or second-place finish.

Why so hot?

It’s summer, of course. But beyond that, there’s a massive drought across the western United States, including much of Texas. At-least-moderate drought affects 86 percent of the state, according to the latest federal drought monitor. Extreme- to exceptional-drought conditions cover 43.8 percent of the state.

The most extreme heat — in interior South Texas — has tended to overlap the zone with the most intense drought.

Even without drought, summer in most of Texas tends to be rather dry, unless there’s a rogue tropical system that brings rain (parts of Southeast Texas, including Houston, will see some welcome rain through Saturday thanks to such a system). The usual summertime dryness is because the jet stream, along which storms track, shifts far to the north, while subtropical high-pressure cells or heat domes swell over the state.

But this year’s heat dome has been unusually persistent and powerful, especially for so early in the year. Scientists have linked the increasing strength of heat domes to human-caused climate change.

The science of heat domes and how drought and climate change make them worse

The average number of yearly 100-degrees days in San Antonio has exploded in recent decades. In the late 1800s, it averaged two such days per year. It currently averages 17. In Austin, this same count has ballooned from an average of eight in the 1940s to 22; in Houston, it has shot up from one in the late 1800s to six.

The hot, dry conditions have increased the risk of wildfires. One large wildfire is currently burning in the state and there is high concern for new blazes around the Fourth of July, when there has historically been a spike in activity in the West.

“The 4th of July is right around the corner,” wrote the National Interagency Fire Center. “Now more than ever, wildland firefighters need your help to prevent wildfires. Remember that fireworks have no place in our wildlands.”

More punishing heat on the way

While the solstice has passed, Texas’s hottest summer weather is typically yet to come.

The graphic below, from climatologist Brian Brettschneider, shows a large area of Texas often sees its hottest temperature in August, unlike many other parts of the country that peak earlier.

In the shorter term, weather models are showing a heat dome rebuilding starting around the Fourth of July. With origins over the toasty Gulf of Mexico, humidity is likely to be high across the eastern half of the state, despite high pressure tending to quash rainfall potential.

After a pause in 100-degree weather for a few days, triple digit heat is projected to return to San Antonio next week. Once this next pulse of heat begins, there is no immediate sign of it abating. It may even turn more extreme by mid-July.

Jason Samenow contributed to this report.

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