A dangerous heat dome is descending on the Midwest and Eastern U.S. this week, threatening to shatter records and expose hundreds of millions to life-threatening temperatures through the July 4 holiday.
Why it matters: Heat is the deadliest weather hazard in the U.S. — and this wave is shaping up to be one of the most widespread of the summer, hitting major cities just as World Cup crowds and July 4 celebrations pack people outdoors.
- 230 million at risk: At least 230 million Americans — roughly two-thirds of the U.S. population — could face extreme heat capable of causing health issues, with overnight lows barely dipping below 80°F in Philadelphia, Baltimore, and Washington, D.C.
- Historic highs possible: Nearly 142 million people are already under NWS heat alerts, with Thursday and Friday carrying the possibility of all-time record highs in cities including Chicago, Kansas City, Nashville, Philadelphia, and Boston.
- Heat indices up to 115°F: Temperatures surge into the 90s and low 100s°F, with humidity pushing heat indices to 100–115°F — and nightly lows in the 70s offering little relief.