As intense heat breaks records around the world, a little-reported fact offers some hope for cooling down cities: Under even the most intense periods of extreme heat, some city blocks never experience heat wave temperatures. How is this possible?

Civilizations have recognized the power of cities to heat themselves up and cool themselves for centuries. City architects in ancient Rome called for narrowing streets to lessen late afternoon temperatures. Narrow streets were found to cool the air by limiting the area exposed to direct sunlight.