Urban heat islands (UHIs) exacerbate thermal stress, disproportionately affecting communities with limited tree cover. While satellite-derived land surface temperature ( \(T{\rm{s}}\) ) is widely used to assess urban heat, it often overestimates conditions compared to air temperature ( \(T{\rm{a}}\) )—the metric more relevant to human thermal comfort. Despite this discrepancy, relatively few studies have leveraged \(T{\rm{a}}\) to quantify the cooling effect of tree canopy in heat-prone areas. Using a citywide network of high-accuracy air temperature sensors and high-resolution satellite data during a heatwave, we first show that surface UHI (SUHI) overestimates urban heat by a factor of two, with SUHI averaging 8.9 °C ± 1.2 vs 4.6 °C ± 1.1 for canopy UHI. We find that tree canopy cover is the dominant cooling factor, explaining 67% of the spatial variation in \(T{\rm{a}}\) . Notably, a 10% increase in tree canopy reduces air temperature by 0.8 °C, while a 30% increase lowers it by as much as 1.5 °C. These findings underscore the essential role of urban greening in mitigating extreme heat, reinforcing the need for targeted tree-planting strategies in vulnerable neighborhoods. By bridging remote sensing with in-situ temperature observations, our study highlights the urgency of integrating air temperature–based UHI assessments into urban planning and climate adaptation policies. Expanding tree canopy coverage is a scalable, nature-based solution for enhancing urban resilience, and this work directly quantifies its impacts.
