Résumé
Understanding microclimatic processes at the street-canyon scale is essential for advancing physical knowledge of urban heat and supporting effective adaptation strategies. This research investigates the influence of irrigated planters, containing climbing and shrub plants, on the microclimate of an experimental street canyon in Montpellier, France, monitored with a dense sensor network. The analysis focused on two heatwave days in August 2023, representative of the Mediterranean climate. Results show that under low wind speeds (<1 m s−1), air temperature variability was mainly controlled by the distribution and intensity of solar radiation. Vegetation had a buffer and retardation effect on the warming of the nearby air regions, with mean air temperature difference between the vegetated and non-vegetated reference zones ranging from −0.17 to 0.44 °C. Comparisons between plant types indicated slightly higher air temperatures (−0.15 to 0.62 °C) and relative humidity increases (1.73 to 1.99 %) near climbing plants compared to shrubs. Irrigation produced no detectable short-term effect on air temperature, while only marginally increasing relative humidity. Thermal comfort assessment using the Universal Thermal Climate Index (UTCI) confirmed that vegetation and irrigation altered microclimatic dynamics but did not substantially reduce heat stress levels for pedestrians. Instead, radiative effects of vegetation and the morphology of the canyon—through shading and surface temperature reduction—were the dominant drivers of thermal comfort modulation in the canyon.