Over a third of US population urged to stay indoors amid record-breaking heat

More than 125 million people under heat alerts as record high temperatures set throughout US, particularly in the south-west

More than 100 million Americans have been advised to stay indoors amid record-breaking heat, with experts warning that such temperatures could become the norm amid the climate crisis.

By Wednesday as many as 107.5 million people, more than a third of the US population, had been warned to stay inside, as a potentially lethal combination of extreme heat and humidity settled over much of the country.