A video by the National Weather Service Las Vegas shows a timelapse of crayons melting under the Nevada sun. The desert city is on track Wednesday to set a record for the fifth consecutive day over 115 degrees amid a lingering hot spell that will continue scorching much of the U.S. into the weekend. A meteorologist says Nevada’s largest city is experiencing the most extreme heat wave in the history of record-keeping since 1937. More than 142 million people around the U.S. are under heat alerts Wednesday, especially in Western states.