From Park-Wide Cooling to Heat Stress Across Activity Spaces: Landscape Effects on Microclimate and Pedestrian Thermal Comfort

As nature-based solutions, urban parks mitigate urban heat, yet park-scale cooling can conceal heat stress within activity spaces. Combining field measurements, spatial analysis, and ENVI-met modeling, we examined landscape–microclimate associations in Mochou Lake Park, Nanjing. During 08:00–18:00, the park interior was on average 1.30 °C cooler than the surrounding built-up area, with relative humidity 2.72 percentage points higher. Nevertheless, the Universal Thermal Climate Index (UTCI) indicated at least strong heat stress at all internal points, and mean air temperature (Ta) differed by up to 2.22 °C among activity-space types. In fitted models, each 10-percentage-point increase in tree canopy cover corresponded to estimated decreases of 0.12 °C in Ta, 1.68 °C in mean radiant temperature (MRT), and 0.44 °C in UTCI, while Ta rose by 0.12 °C per 10 m of distance from the lake. Open space ratio was associated with higher MRT and UTCI, and near-ground permeability ratio with lower UTCI under the study-day wind conditions. A tree canopy cover of approximately 40% in activity spaces emerged as a case-specific, model-derived reference value at which the predicted daytime maximum UTCI remained below the 46 °C extreme heat stress threshold. These findings reveal thermal risks hidden by park-scale averages and can inform climate-adaptive park design.