WASHINGTON, United States (AFP) — Blistering temperatures and humidity gripped swaths of the United States on Wednesday, with the worst yet to come for the densely populated East Coast as the nation co-hosts the World Cup and prepares to celebrate its 250th birthday.

“Heat dome” conditions — in which high-pressure systems trap warm air over a region like the lid on a pot — persisted over the Midwest and South and were moving to the east, with some 46 million people currently under heat alerts.

“We are entering what could be the most extreme heat wave this city has seen in over a decade,” New York Mayor Zohran Mamdani said in a video, adding that he wanted to make sure people stayed safe while watching the World Cup, celebrating July Fourth “or, renting out MSG to get married, hypothetically.”