Key keywords: 2024 U.S. summer heat wave, 115°F feels like heat index, National Weather Service heat advisory, heat-related illness prevention, U.S. Southwest extreme heat, urban heat island effect, power grid strain warning The National Weather Service (NWS) has issued widespread heat advisories and excessive heat warnings across 28 U.S. states this week, as a historic, unseasonably early heat dome settles over most of the contiguous United States, bringing record-breaking high temperatures and dangerous humidity levels that will push 'feels like' heat indexes to 115°F or higher in dozens of major metropolitan areas. Forecasters note that the heat event will first impact the Southwest, where cities including Phoenix, Arizona, Las Vegas, Nevada, and Albuquerque, New Mexico, will see daytime high temperatures stay above 110°F for 5 to 7 consecutive days, with overnight low temperatures failing to drop below 85°F, offering no relief for residents without access to air conditioning. In desert regions, low humidity means actual temperatures will closely align with heat index readings, with some remote desert locations expected to hit 122°F by midweek. The heat wave will then expand eastward to the Southern Plains and Deep South by Wednesday, where high humidity paired with 95°F to 103°F actual high temperatures will create far more dangerous conditions. Cities including Dallas, Houston, San Antonio, Memphis, and New Orleans will register heat indexes between 110°F and 118°F for 3 to 4 consecutive days, raising the risk of rapid heat exhaustion and heat stroke even for healthy adults spending more than 15 minutes outdoors. Local governments across affected regions have rolled out emergency response measures to protect vulnerable populations, including opening 24/7 cooling centers in public libraries, community centers, and fire stations, waiving public transit fares for residents traveling to cooling sites, and extending operating hours for public swimming pools. Utility providers have also issued warnings of potential rolling blackouts, as power demand from residential and commercial air conditioning use is projected to hit all-time summer highs in 17 states. The NWS has urged all residents in warning zones to avoid outdoor activities between 10 a.m. and 6 p.m., drink 8 to 10 ounces of water every hour even if not thirsty, check on elderly, disabled, or unhoused neighbors at least twice a day, and never leave children, pets, or vulnerable adults unattended in parked vehicles, where internal temperatures can rise to 120°F in less than 10 minutes even with windows cracked open. Public health officials also noted that unhoused populations and residents living in low-income neighborhoods with high concentrations of asphalt and limited tree cover (a phenomenon known as the urban heat island effect) are 2 to 3 times more likely to experience heat-related illness than residents in wealthier, tree-lined suburban areas.