This work proposes a simplified methodology to obtain the needed data to determine and investigate the variation of photovoltaic modules performance under non-standardized environmental conditions-Standard Test Conditions and Nominal Operating Cell Temperature. This methodology uses a previously developed mathematical model in association with environmental parameters as wind speed, air temperature and irradiance in different cities, located in different regions in Brazil. These data are obtained from both SWERA project and the National Institute of Meteorology of Brazil websites, both of them with free access on the internet. The result of this methodology is the operating temperature of a commercial polycrystalline module of 330 Wp and 1.95 m², and this methodology also results in the maximum power of the module and efficiency for each set of analyzed environmental parameters. As conclusion, from the the results, it is possible to suggest the investigated environmental parameters have a significant impact on the module performance and therefore cannot be neglected.