The street on the right is 12°C cooler than the street on the left. Same sun, same asphalt, same afternoon. The canopy above it is doing the work of ten air conditioners per tree, and the electricity bill is zero. A mature street tree transpires 100 to 400 liters of water on a hot day. Evaporating one liter of water absorbs 2,260 kilojoules of heat energy straight out of the surrounding air. Run that through a single large tree and you get 70 kWh of cooling capacity per day. Wageningen University measured the live output at 20 to 30 kilowatts while the sun is up. A window AC unit runs at 2.5 kW. One street tree equals ten of them. Shade accounts for about 70% of the cooling. The other 30% is pure thermodynamics. Water molecules can't turn into vapor unless something hands them energy, and that energy comes out of the surrounding air. Every leaf on a canopy tree is a heat pump with no electricity bill. Then look at the ground. 46°C asphalt causes second-degree burns on bare skin in under 35 seconds. It also radiates stored heat into the apartments above it all night, which is why streets without canopy stay warm after sunset. The Camden, New Jersey sensor study found intersecting tree canopies were the only vegetation type that produced statistically meaningful air cooling above 30°C. Grass didn't. Shrubs didn't. The canopy has to actually close over the street. A Nature Communications meta-analysis of 182 studies across 110 cities put the ceiling at 12°C of pedestrian-level air cooling under dense canopy. The right side of the photo is hitting the upper bound of what physics allows. Heat is the deadliest weather event in the United States. 20% of natural hazard mortality. Cities spent 70 years removing the cheapest cooling system ever invented and replacing it with electric units that exhaust hot air into the street, making the outside hotter to keep the inside colder. The right side of that photo built its HVAC 40 years ago. It runs on rain.