Abstract. Bucharest Municipality and its surroundings are situated in the South-Eastern part of the Romanian Plain in a temperate-continental climate, characterized by a continentalization tendency as a result of the climatic influences of transition in the West and excessive in the East. Therewith, one can identify remarkable differentiation between the urban space and the adjacent periurban space related to the manifestation of the heat island, which can be identified within the atmospheric space. The paper is based on statistical-climatologic analysis of the data issued from simultaneous microclimatic and topoclimatic measurements (air temperature and relative humidity of moist air) which permitted the identification of the heat island of Bucharest Municipality. The topoclimatic mapping of the horizontal profile of the values of these climatic parameters was achieved within peculiar season and weather types (serene and calm days; serene and windy days; cloudy or overcast sky and calm days; cloudy or overcast sky and windy days). The most significant thermal and hygric differentiation between the urban and suburban areas appear during summer and winter seasons on serene and calm days (without atmospheric dispersion) during morning and noon.The distribution maps of the couple air temperature/relative humidity of moist air within the above mentioned season and weather conditions defines an urban core with higher temperature and lower humidity values comparing to the suburban area. The shape and the scale of the heat island are mainly related to the seasonal variations, being in direct proportion with the spread of the urban area as a result of the high changes of the urban ecosystem.