>> reporter: in phoenix, there hasn't been a day cooler than 110 degrees this month. with excessive heat warnings expect today last through at least next week. adding to the danger, red flag warnings as this southwest braces for what could be yet another grueling record-breaking heatwave. what is driving this dangerous heat across the country? >> yeah, in a word, human-caused warming. you make the planet hotter, you get more frequent, intense, long lasting heatwaves. we should expect the unexpected. >> reporter: michael mann and other scientists warn kari lake could trigger monday devastating ...