In 2013, Paris tested spraying non-drinking water on sun-baked streets; wet pavement was up to 23°F cooler, but the effect faded as the surface dried

Long before anyone worried about climate change, Parisian street cleaners doused the city's pavements with water every morning, a practice dating back to the late nineteenth century that was originally meant to keep dust down rather than cool anyone off. That habit faded through the twentieth century as cleaning methods changed, and the practice became a historical curiosity.

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