Heatwaves Enveloping News Today

Disease, bringing new hope to millions. >> announcer: this is "nbc nightly news" with lester holt. >> good evening, and welcome, everyone. it would be easy to dismiss the heatwaves enveloping parts of the country as simply the price of summer. but the extreme temperatures and durations we are seeing are part of a disturbing trend worldwide as scientists say the planet is seeing some of its warmest days on record. here at home, some 24 million people are living under heat alerts. the temperatures...