Heat Dome Takes 3-Digit Temperatures to Texas, Testing Grid

A heat dome inflicting extreme temperatures on southwestern states arrived in Texas on Wednesday, prompting warnings of the danger to residents as the grid hits record demand. The same dome brought almost 90 straight days of three-digit highs to Phoenix. In central Texas, the National Weather Service predicted an extended duration for the heat "with little to no overnight relief," the Guardian reports. About 14.7 million people already are under an excessive heat warning, per the AP, with heat indexes expected to top 110 degrees Fahrenheit in places. About 10 million more are under a heat advisory.

The slow-moving heat domes occur when strong, high pressure traps hot air over an area, which keeps cool air from traveling in. Temperatures on the ground increase and remain high. "It is usually sunny, the sun is beating down, it is hot and the air is contained there," said meteorologist Bryan Jackson. San Antonio, Corpus Christi, and Amarillo are among the places expecting record highs. The dome should eventually move into the mid-Mississippi Valley, where it could weaken slightly, Jackson said.

Wildfire activity is increasing, and Gov. Greg Abbott dispatched crews and urged Texans to take precautions. An EMS officer said said heat-related illness in the area around Austin is up this summer. "The vast majority of what we see is heat exhaustion, which is good because we catch it before it's heat stroke," said Capt. Christa Stedman. "But it's bad because people are not listening to the red flags," which include heat cramps in the arms, legs, or stomach.

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Demand on the Texas power grid hit a record high on Tuesday, topping the mark reached last August, per the Dallas Morning News. The Electricity Reliability Council of Texas had predicted that August would be a strain on its grid. The system mostly was holding up Wednesday, though there were outages in Harris County, per the Austin American-Statesman. Improved solar power capacity and battery storage are helping, per Axios. (More heat dome stories.)