Meanwhile, millions of people are under heat advisories in the US cities of Boston, New York, Philadelphia and as far west as Buffalo, New York, which will last through Wednesday.

The Northern Plains, Midwest and Northeast will be hardest hit, with temperatures in Chicago forecast to reach 97°F on Wednesday.

New York could reach 100F, while Washington DC expects 102F. Some places could get even hotter, and high humidity is expected to make it feel even more uncomfortable.

Earlier this week, the Montana city of Billings hit 111F, where its previous heat record was 108F. In Utah’s Salt Lake City, the previous record of 107F was broken when it reached 109F.

The high temperatures come shortly after an unprecedented Fourth of July heat wave hit much of the United States.

More than 165 million people suffered record temperatures along the East Coast and Midwest of the United States, and at least 44 deaths were reported.

The heat also disrupted Fourth of July celebrations, including the Washington DC parade, which was cancelled.

Heat waves have become more frequent, more intense and longer lasting due to human-induced climate change. The world has already warmed around 1.1°C since the industrial age began and temperatures will continue to rise unless governments around the world make big cuts in emissions.