A prolonged and dangerous heat wave driven by a heat dome is intensifying across a large swath of the central and eastern United States this week, bringing scorching daytime temperatures, high humidity and stifling overnight conditions ahead of the July 4 holiday weekend, the National Weather Service said. Approximately 120 million people nationwide are under extreme heat warnings as of Tuesday, according to the agency.
Temperatures ranging from 95°F to 105°F (35°C–40.6°C) combined with high humidity will produce heat index values of 100°F to 115°F (38°C–46°C), the weather service said. Daily temperature records are expected to be broken on Thursday and Friday, with some monthly and all-time records possible. Officials urged residents in affected areas to limit time outdoors, stay hydrated and ensure access to air conditioning or cooling centers.
New York City Mayor Zohran Mamdani activated a heat emergency plan with hundreds of cooling centers set to open across the city Wednesday. In Detroit, where temperatures could reach 100°F (38°C), officials opened a dozen recreation centers with air conditioning for residents seeking relief.
The heat wave is also affecting FIFA World Cup matches being played in U.S. cities. Philadelphia is moving parts of its Fan Festival into cooled tents on Thursday and Friday. The global players’ union Fifpro considers heat indexes exceeding certain thresholds too unsafe for play, and some match locations — including Atlanta, Houston and Arlington — could see conditions that approach or exceed those thresholds, particularly for fans traveling to and from air-conditioned stadiums. The England v DR Congo match scheduled for Wednesday in Atlanta is among those affected.
In Canada, the heat wave extends into Ontario, where temperatures could reach 37°C (99°F) this week, Environment Canada said. The agency has issued orange heat warnings — the second level of a three-tier alert system — across parts of Ontario. Toronto is set to host a World Cup match Thursday, when temperatures are expected to reach 35°C (95°F). Central and eastern parts of Ontario, including Montreal, are under yellow heat warnings, the lowest level.
The U.S. heat wave follows an unprecedented early-summer heat wave across Europe that scorched several countries in recent days. The World Health Organization said it was linked to 1,300 deaths.