Heatwaves: About 82 percent of the U.S. population are likely to experience temperatures topping 90 degrees

UNITED STATES — More than 55 million people across the nation were under an alert for extreme heat on Sunday and through most of the week ahead as temperatures are forecast to hit triple digits in some parts of the country. Over the next seven days, 265 million people, or about 82% of the U.S. population, are likely to experience temperatures topping 90 degrees as the official first day of summer arrives on Thursday... abcnews.go.com