"On any hot day in the Phoenix area, the heat builds up in some neighborhoods more than others.
In leafy neighborhoods with trees and shade, the air stays cooler and more bearable. But in exposed areas where the sun beats down on pavement and concrete, the heat soars.
Research has shown these differences in many areas fall along lines of race, ethnicity and income, reflecting the nation’s history of discrimination in housing and decades of disinvestment in poorer neighborhoods.
Now researchers have looked closely at 20 urban areas across the Southwest and have found that the poorest 10% of neighborhoods are much hotter — 4 degrees F on average — than the wealthiest neighborhoods in the same areas."