Even in the hot arid deserts of Arizona and the humid tropical environs of Florida, trees can play a big part in keeping the populace cooler in seasons when the heat rises. With a growing number of days each year when temperatures climb above 90 degrees in the southern and southwestern U.S., the shade provided by trees can be one of the best ways to keep people comfortable outdoors, says Fulton Schools Assistant Professor Ariane Middel, an urban climatologist. But not all kinds of trees do the job. Urban planners should examine how effectively the canopies of particular tree species will perform in their cities’ specific environmental and climatological conditions. The report also aired on ABC Channel 7 News Denver.