Plastic components of a vehicle are strongly affected by external environmental conditions. High temperatures can damage the components, influencing the behavior of other parts of the vehicle. In this work, the influence of temperature and weather conditions of the plastic components is evaluated. Results of tests of thermal fatigue carried out in laboratory are correlated with thermal solicitations obtained under several critical environmental conditions. Weather maps from several regions of Brazil were evaluated in order to identify critical conditions, and a vehicle was submitted to these critical ambient conditions. Ambient temperature, solar radiation and temperature of the plastic components were measured and compared with solicitations currently reproduced in laboratory. The maximum temperature values achieved by the components were determined, allowing the critical evaluation of the materials used in the car. Also, the comparison between laboratory and field results permitted a revision of the current adopted.