This paper aims to present the evaluation of wet weather contribution to the total annual pollutant load in a residential watershed of 125 ha in Belo Horizonte, Brazil. The monitoring was done over a full hydrologic year, covering diurnal variations during dry periods and frequent samplings during rain events. The paper discusses the changes in fluxes of major pollutants and the contribution of selected micro pollutants. The results show that the concentrations of the major constituents are impacted by the discharge of untreated waste water, and that the values do not comply with the Brazilian legislation for water bodies. For most of the water quality parameters, the concentrations decreased during rain events due to dilution, with the exceptions of suspended solids and some heavy metals, which increased. This increased load is due to erosion and sediment resuspension.