A vast and oppressive heat dome has descended on the eastern half of the United States, placing more than 180 million people from the Great Plains to the Atlantic coast under extreme heat warnings or advisories, according to the US Weather Prediction Center.

Temperatures in New York City’s Central Park reached 100°F (38°C) on Thursday, the hottest day there since 2012, while records were set from Caribou, Maine, to Chattanooga, Tennessee. The heat index—a measure combining temperature and humidity—is forecast to exceed 110°F (43°C) in several cities, with Washington and Philadelphia potentially feeling like 115°F (46°C). The strain on power infrastructure is acute: the PJM Interconnection, the grid serving 65 million people from Washington to Chicago, declared an emergency for a third consecutive day, ordering all power plants to maximum output. More than 71,000 customers were without electricity early Friday, and Consolidated Edison in New York asked 133,000 Brooklyn households to conserve energy while crews repaired equipment, reducing voltage by 8%.

The heat wave coincides with the 250th anniversary of US independence celebrations and the ongoing FIFA World Cup, forcing event organisers to adapt. In Boston, the opening of a fireworks display was delayed; Philadelphia shortened a parade and cancelled a street party. The players’ union FIFPRO called for match delays, citing unsafe conditions, and FIFA has mandated three-minute hydration breaks. The France-Paraguay match in Philadelphia on Saturday is expected to begin with a wet-bulb globe temperature above 28°C, a threshold considered dangerous for athletes.

While no heat-related fatalities have been confirmed by authorities, officials across the region warn that the combination of prolonged high daytime temperatures and unusually warm nights—New York may not drop below 80°F (27°C) for three consecutive nights—poses a severe health risk, particularly for the elderly and those without adequate cooling. The heat dome is expected to persist through the weekend before a shift in the jet stream potentially brings relief, though that same shift could trigger severe thunderstorms and flash flooding in parts of the Midwest and Northeast. The situation remains under close monitoring by federal and state emergency services.