WASHINGTON (UNITED STATES) - 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 like the lid on a pot -- persisted over the Midwest and South and were moving east, with some 46 million people under heat alerts.