The aim of this work was to characterize and to bring into relationship of the net radiation with the latent heat flux equivalent to water (mm) in a patch of Atlantic Forest within the metropolitan area of Sao Paulo (RMSP). The estimation of the latent heat flux (LE) was made by the energy balance equation with the Bowen ratio. Measurements of net radiation and psychometrics gradients were made. Soil heat flux (G) was measured by temperature sensors in two depths. Measurements were made at Park of Science and Technology of Sao Paulo University (CIENTEC), Sao Paulo, Brazil, between 2011 and 2013. Results indicated that evapotranspiration varies seasonally and the amount of water evaporated exceeds 3.0 mm·day^-1 in spring/summer and in autumn/winter the amount is approximately 1.0 mm·day^-1. The evapotranspiration is increased under RMSP urban climate conditions with higher air temperature and lower moisture especially in summer season.