A heat dome covering the US’s south-west region is affecting nearly 23 million Americans, bringing with it some of the highest temperatures of the summer and putting pressure on the electrical grid in Texas. The heat dome phenomenon occurs when strong, high pressure traps hot air over a region, preventing cool air from traveling in and causing temperatures to rise on the ground and stay high. Those in central Texas are experiencing extreme heat for a long duration, “with little to no overnight relief”, according to the National Weather Service. Temperatures are expected to reach up to 110F (43C). San Antonio may experience its hottest temperature in more than 10 years on Wednesday. The dry heat is also setting off wildfires, prompting the Texas governor, Greg Abbott, to deploy additional firefighting resources to parts of the state. Abbott said: “Texans are strongly urged to take all necessary precautions and heed the guidance of state and local officials to keep their families and their loved ones safe from wildfires. I thank the Texas division of emergency management and local emergency management personnel for their work as they prepare for potential wildfires across the state.” Texas A&M forest service says wildfire activity is expected to increase across north-west and central Texas due to dry vegetation caused by triple-digit temperatures. The extreme weather is pushing the state’s already unreliable electrical grid to its limits, with many of its 27 million energy customers cranking up the air conditioning in their homes and businesses to cool down. Earlier this summer, more than 800,000 Houston residents went without power for days during a heat advisory after Hurricane Beryl downed power lines in the state. In Phoenix, Arizona, the high temperature was 112F on Tuesday afternoon – just one degree less than the record breaking temperature of 113F set in 2019. Those under the heat dome are advised to avoid strenuous outdoor activities, stay hydrated, and wear sunscreen and light-colored clothing. For those who work outdoors, it is recommended to work early or very late in the day. Extra precautions should be taken for vulnerable populations such as children, the elderly and disabled. States including Texas, New Mexico and Arizona, have set up several cooling centers in preparation for the extreme weather. Heat is the leading cause of weather-related fatalities in the US. “Approximately 1,220 people in the United States are killed by extreme heat every year,” the Centers for Disease Control and Prevention says. The climate crisis, caused in part by the burning of fossil fuels, forest destruction and methane emissions, means heatwaves are increasing “in frequency, duration, intensity and magnitude”, according to the World Health Organization.