A heat dome has intensified across the United States, prompting forecasters to issue weather warnings covering more than 80 million Americans. The extreme heat event highlights growing concerns over the frequency and severity of prolonged hot-weather episodes affecting large swathes of the country.

Meteorologists have flagged the scale of the warnings as significant, given the tens of millions of people falling under alerts as the heat dome strengthens. The full details of affected regions, expected temperatures and duration were not available in the source material retrieved for this summary.