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Urban tree canopy coverage has become a focal point for city planners seeking low-cost strategies to mitigate rising summer temperatures. A multi-year monitoring project across eighteen neighborhoods in a single metropolitan region measured surface and air temperatures alongside canopy density, aiming to quantify the cooling effect of street trees under real-world conditions rather than laboratory models. Researchers recorded that neighborhoods with canopy coverage above thirty percent experienced average midday temperatures approximately four degrees Celsius lower than neighborhoods with coverage below ten percent, a gap that widened during heatwave periods to as much as six degrees. The cooling effect was attributed primarily to shading and to transpiration, the process by which trees release water vapor that cools surrounding air. Beyond temperature, the project documented a measurable reduction in emergency room visits for heat-related illness in higher-canopy neighborhoods during the hottest weeks of summer, along with modestly lower residential energy consumption for air conditioning. However, the researchers also noted a troubling pattern: canopy coverage correlated strongly with neighborhood income, with lower-income areas averaging less than half the tree cover of wealthier districts, largely a legacy of historical infrastructure investment and housing development patterns dating back decades. This disparity meant that residents least able to afford cooling costs or relocate during extreme heat were also those most exposed to it. The project's authors recommended that municipal tree-planting budgets be reallocated to prioritize historically underserved neighborhoods first, arguing that equitable canopy expansion would deliver the greatest public health benefit per dollar spent, though they acknowledged that trees take years to mature and deliver full cooling benefits.