Millions of Americans are facing major heat waves with temperatures consistently exceeding 90 degrees. In big cities, the heat hits hardest for people of color and low-income residents. In New York, Black residents die from heat stress at double the rate of white residents. Advocates and experts trace the phenomenon back to decades of discriminatory housing policy, especially redlining. That was the 1930s government practice of rating neighborhoods’ investment worthiness using race as a determining factor and denying mortgages to minority buyers. The labeling of minority neighborhoods as risky restricted resources for generations. It also starved those areas of parks and trees and affected how residents experience heat today.