On a hot day in February 2024, volunteers dispersed across Cape Town, South Africa, with sensors affixed to their cars. Their aim was to measure heat differences across the city. In Cape Town's dense, highly developed center, they recorded air temperatures as high as 41.6 degrees C (106.9 degrees F). Informal settlements like Joe Slovo, just north of the city center, were nearly as hot. Yet, leafier residential areas southeast of downtown barely broke 25 degrees C (77 degrees F).