However, Arizona is home to the two deadliest weather phenomena in the U.S.: Extreme Heat and Flash Floods. Here is why Cochise County should be more concerned about extreme heat and flash floods than a tornado warning. According to NAOO and the CDC, extreme heat kills more than 800 people each year, and flash floods kill between 80 and 100 people annually. Extreme HeatWhile Flash Floods are sudden and powerful, extreme heat is silent and much deadlier, killing over 500 people annually in Arizona alone. Heat and floods may not be the most dramatic weather concerns, but they are the deadliest.