We used outdoor test cells during a hot humid period to analyse the surface temperatures behind the following four types of green walls: a felt layer wall; a planter boxes wall; a direct climbing plants wall, and; an indirect climbing plants wall. We compared these temperatures with temperatures of a bare wall and we found that all four types of green facades were able to maintain lower temperatures than the bare wall, and that the felt layer and planter boxes wall had lower temperatures than the other walls for the majority of the study period. In particular, the daily average and peak surface temperatures behind the felt layer wall were by 1.9 °C–4.8 °C and by 7.1 °C–13.4 °C respectively lower than the bare wall. We undertook a significance analysis and produced Pearson coefficients to better understand the relationship between average daily weather conditions and the surface temperatures on all five test cells. We noted that the average daily solar radiation flux did not affect the surface temperatures behind the planter boxes and felt layer walls, but the daily average ambient air temperature was significantly correlated with the average and peak surface temperatures behind all four green facades. Finally, we concluded that the cooling potential of the felt layer and the planter boxes walls increases with higher amounts of solar radiation and higher ambient temperatures. In addition, from the analysis of the diurnal temperature variations and the time series trends we illustrated that the temperatures behind the felt layer and planter boxes walls fluctuated less than the other walls, which lead to a slower rate of surface temperature reductions during a cooler day than the other wall types of the study.