Lightning strikes the Willis Tower (formerly Sears Tower) during a summer thunderstorm in downtown Chicago. (Scott Olson/Getty Images) At a Glance Climate change is making summer weather systems weaker.Weaker systems means pollution could linger in cities longer, instead of being cleared out quickly.Heat waves could also last longer.At the same time, thunderstorms are more destructive. Climate change is altering North America's summer weather systems in a way that could mean more lingering pollution, stronger thunderstorms and longer heat waves, a...