Millions under heat alerts in U.S. as temperatures rise

Millions are at risk for severe weather from Mississippi to upstate New York. The South is dealing with unrelenting heat while Alaska suffered a weekend of flooding. » Subscribe to NBC News: » Watch more NBC video: NBC News Digital is a collection of innovative and powerful news brands that deliver compelling, diverse and engaging news stories. NBC News Digital features , , , Nightly News, Meet the Press, Dateline, and the existing apps and digital extensions of these respective properties. We deliver the best in breaking news, live video coverage, original journalism and segments from your favorite NBC News Shows. Connect with NBC News Online! NBC News App: Breaking News Alerts: Visit : Find NBC News on Facebook: Follow NBC News on Twitter: Get more of NBC News delivered to your inbox: #Heatwave #Weather #Heat