ABC News' Ginger Zee breaks down the biggest dangers of extreme heat, which is considered the deadliest weather-related hazard in the U.S., according to the Fifth National Climate Assessment. ––– Subscribe to ABC News on YouTube: https://abcnews.visitlink.me/59aJ1G ABC News is your daily source of breaking national and world news, exclusive interviews and 24/7 live streaming coverage. Download the ABC News app for the latest headlines and alerts: https://abcnews.go.com/devices Watch 24/7