text:  From NPR News, this is All Things Considered. I'm Ari Shapiro in Washington. And I'm Elsa Chang in Culver City, California. One of the world's most challenging cycling races is underway right now. The Tour de France will cover more than 2,000 miles. And this summer, riders will not only have to contend with the hills, but also with the heat. In a few minutes, we'll talk about how the hot temperatures are affecting the race.