Thermal comfort during hot days in Munich, Germany: How does vegetation structure in small urban greenspaces matter?

• Small greenspaces can buffer extreme heat stress by up to 16 °C mPET on hot days • Vegetation structural complexity is a key driver of thermal comfort in small parks • Vegetation structure affects mPET directly and indirectly via sky view factor • Mature trees with tall canopies provide the strongest mPET buffering in small parks • Shading drives fine-scale thermal variability Urban greenspaces play an increasingly important role in urban planning and public health, particularly in providing thermal comfort during hot summer days. While the cooling potential of greenspaces generally increases with size, it also strongly depends on vegetation structure, particularly in small greenspaces. Optimizing these spaces for thermal comfort requires a clear understanding of how their vegetation structure shapes local cooling. Based on field measurements in 2024, we modeled the modified Physiologically Equivalent Temperature (mPET) across 12 structurally diverse small greenspaces (< 2 ha) in central Munich, Germany, and in their built surroundings. High-resolution vegetation structure derived from mobile terrestrial laser scanning was combined with sky view factor estimates from hemispherical photographs and micro-meteorological measurements. Using mixed-effects models and structural equation modeling, we assessed both direct and indirect pathways linking vegetation structure, sky openness, shading, and thermal comfort. Our results show that small greenspaces can reduce mPET by up to 16 °C compared to built surroundings. Vegetation structure emerged as a key determinant of this buffering capacity: greenspace plots with tall, multi-layered vegetation provided strong mPET buffering, whereas sparsely vegetated plots offered little to no thermal relief. Mean canopy height was the strongest predictor of mPET buffering, and vegetation structure influenced thermal buffering both directly and indirectly through reductions in sky view factor. At finer spatial scales, shading dominated local thermal variability, with shading effects being strongest in structurally complex plots. These findings highlight that small but structurally complex greenspaces can play a vital role in climate-adaptive urban planning.