Extended heat wave threatens public health and transportation across the Eastern United States

A high-pressure system that meteorologists compare to the 1995 and 2011 events is trapping hot, humid air over the Northeast and Midwest, producing temperatures close to 100 °F on Thursday and Friday and a heat index that could reach 110-115 °F.

"When you’re talking about two to potentially four days where you’re right around 100 degrees, that’s unusual," said meteorologist Mr. Vaz. The prolonged heat raises the risk of heat-related illnesses, with emergency-room visits increasing sharply once the heat index exceeds 95 °F and spiking further above 105 °F, according to regional health data. Officials warned that the timing of the heat wave over the Fourth of July holiday could expose more people to dangerous conditions, especially at outdoor gatherings and World Cup viewing parties. Coastal areas are expected to remain cooler, with sea breezes keeping beach temperatures in the mid-80s, but lifeguards have issued a moderate to high rip-current warning for the weekend. Public health experts emphasized prevention: stay hydrated, limit outdoor activity during peak heat, wear light-colored, loose clothing, and seek air-conditioned spaces. "Drink more water than you think you need," advised Dr. Bradley Uren, an emergency-medicine professor. "Once you feel thirsty, you’re already behind," added Dr. Reed Caldwell of NYU Langone. Cooling centers are being opened in many cities, and libraries, malls and other public buildings are recommended as temporary refuges. Air-conditioning technicians in the Chicago area reported a surge in emergency service calls as systems strain under the heat, with some businesses expecting one of their busiest weeks of the year. Mayor Brandon Johnson urged residents to protect themselves, recommending light clothing and closed shades, while the National Weather Service projected the worst of the heat wave to continue through Thursday with heat indexes near 105 °F. Health officials also reminded the public to monitor vulnerable groups—older adults, infants, pregnant women and people with chronic conditions—and to watch for signs of heat exhaustion or heat stroke, which require immediate medical attention.