Air temperature measurements under the vegetation canopy of trees in suburban streets and at reference points were carried out under mostly light wind conditions in five streets in the city of Athens (Greece) during a short exceptionally hot weather period in 2007. The average cooling effect at 1400 h (LST) was found to range from 0.5 to 1.6 degrees C and at 1700 h (LST) from 0.4 to 2.2 degrees C; the highest cooling effect of 2.2 degrees C was found to be reached in a street with high tree shaded area and minimal traffic load. These results imply the passive cooling potential of shade trees. The trees cooling effect values obtained for Athens, however, were found to be lower than the ones reported in similar studies in the Mediterranean region. In terms of residential energy implications, the elaboration of the results using simplified assumptions showed that the current level of tree cover in the examined streets may reduce summer time consumption for air conditioning during the day by 2.6-8.6% and during peak hours by 2.9-9.7%. (C) 2010 Elsevier Ltd. All rights reserved.