US heat wave warnings cover 44 million people

About 44 million Americans were under heat wave warnings on Saturday as temperatures in the Rocky Mountains and northern plains were expected to reach 110F over the weekend, the National Weather Service said.

The weather service warned that temperatures well above seasonal averages could break records. Its Weather Prediction Center said dangerous heat was expected through the weekend, with triple-digit highs and potential daily maximum temperature records on both days.

Sunday was expected to be the hottest day, with temperatures forecast to reach between 100F and 110F in several northern states, including Montana and North Dakota. Salt Lake City was expected to experience unprecedented heat.

The heat also hindered efforts to fight large wildfires in Colorado and Utah. Hot weather was also affecting the southeastern United States, including Miami, which was hosting the England-Norway World Cup quarterfinal match on Saturday.

The eastern United States had been gripped by another heat wave a week earlier, with temperatures reaching around 104F in New York and Philadelphia.

Heat waves are becoming more common and intense because of climate change, primarily driven by the burning of coal, oil and gas and the emission of greenhouse gases.