A sprawling heat dome parked over the central and eastern United States has driven temperatures to levels not seen in more than a decade, triggering heat advisories and warnings for roughly 160 million people from Texas to Maine, according to the National Weather Service. Meteorologists said the high-pressure ridge is trapping hot, humid air and pushing heat indices above 110 °F (43 °C) in several major cities. The mercury reached 100 °F (38 °C) in New York City on Tuesday, the first triple-digit reading in the city since 2012. Boston climbed to 101 °F, while Newark, New Jersey, hit 103 °F, and Washington, D.C., was forecast to match Boston’s mark. The Weather Service said hundreds of daily temperature records have fallen since the weekend and warned that more than 250 additional cities could set new highs as the event peaks. Authorities across the region moved to blunt the impact. New York Governor Kathy Hochul declared an emergency in dozens of counties and opened cooling centers; Philadelphia issued a heat-health emergency; and Amtrak slowed trains on the Northeast Corridor between noon and 8 p.m. to protect rail infrastructure. Con Edison urged customers to conserve power after an outage in the Bronx cut electricity to about 34,000 homes, and several school districts in upstate New York shifted to half-day schedules. Extreme heat is the deadliest weather hazard in the United States, and scientists say human-driven climate change is increasing both the frequency and intensity of such events. Summers are now about 2.4 °F warmer nationally than they were 50 years ago, government data show. Forecasters expect the dome to weaken after a cold front sweeps through the Northeast late Wednesday, with daytime temperatures predicted to fall by as much as 30 °F in some areas by Friday. Until then, health officials continue to urge residents to limit outdoor activity, stay hydrated and check on vulnerable neighbors.