A combination of high humidity and temperatures above 90 degrees Fahrenheit (32 degrees Celsius)could push heat index values above 115 in some parts of the South this weekend, contributing to atmospheric instability and creating conditions ripe for more harsh storms, weather service meteorologist Matt Mosier said. The agency issued excessive heat warnings affecting millions of people in parts of southern Louisiana and Texas, saying the heat index could reach 110 degrees. South Florida and Mississippi were under heat advisories for Friday. While Southern states are accustomed to high heat, extreme weather conditions have become more frequent across the country and with more intensity, driven by climate change, scientists say. At least three people were killed and dozens injured by tornadoes in Perryton, Texas, on Thursday.

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Persons: Matt Mosier, It's, Power, Poweroutage.us, Davis Wood, Tyler Clifford, Jonathan Oatis Organizations: U.S, National Weather Service, Thomson Locations: Texas, Florida, Louisiana, Mississippi, Perryton , Texas, Pensacola , Florida, Escambia County, Warrington, New York