The study had the objective of assessing the seasonality of Aedes albopictus and the impact of environmental factors on breeding sites in a protected urban area. Immature individuals were collected through fluid aspiration from nine tree holes, in the Ecological Park of Tietê in the city of S?o Paulo, Southern Brazil, from 2001 to 2002. The index of positivity and number of individuals results were as follows: positivity x precipitation (rho=0.69, p<0.001), positivity x temperature (rho=0.35, p<0.001), number of individuals x precipitation (rho=0.29, p<0.001) and number of individuals x temperature (rho=0.13, p<0.05). These correlations suggest rainfalls had greater impact than temperature.