The blistering heat will sear down across the southern US and northern Mexico, challenging local records. Temperatures in Phoenix may reach 109F Sunday and as high as 114F across the region. Residents have been urged to stay indoors and seek air conditioning.
Readings will reach similar levels across the Mexican states of Baja California, Sonora, Chihuahua, Coahuila, Nuevo León and Tamaulipas bordering the US. In addition to the daytime highs, overnight low temperatures will stay warm enough to break records in many places, putting more pressure on fragile power systems.
“The temperatures of 100 degrees are going to expand,” said Andrew Orrison, a forecaster at the US Weather Prediction Center. “The big story is the expanding heat wave across the South.” Record-breaking heat taxed energy grids in both Mexico and Texas in June, with power outages popping up and the threat of rolling blackouts rising as officials tried to manage supplies. A surge of deaths across northern Mexico were blamed on excessive heat.
Del Rio, Texas, near the border with Mexico, set 12 daily temperatures records, including 11 in a row, as well as posting its all-time hottest day of 115F on June 21, according to the NWS. Austin, the state capital, is forecast to hit 102F Sunday and 103F for the rest of the week. By Wednesday, Dallas is forecast to reach 102F and Houston will be in the high 90s through the week with humidity making it feel much hotter.