A new study says that black people living in most US cities are subject to double the level of heat stress as their white counterparts.
The researchers say the differences were not explained by poverty but by historic racism and segregation.
As a result, people of colour more generally, live in areas with fewer green spaces and more buildings and roads.
These exacerbate the impacts of rising temperatures and a changing climate.
Cities are well known magnifiers of a warmer climate.
The surface urban heat island effect is the technical term for the impact that the buildings, roads and infrastructure of cities have on temperatures.
All that concrete and asphalt attracts and stores more heat, ensuring that both days and nights in big urban areas are much warmer than the surrounding locations.
But, within cities, there are often large differences in this heat island impact, with areas rich in trees and green spaces noticeably cooler than those that are dense with housing and industry.