The quantification of the influence of the weather conditions has a great importance in the field of Structural Heath Monitoring (SHM). In this work, the KTH two-span post-tensioned concrete bridge is studied. A shell based Finite Element (FE) model and a 3D solid FE-model are made. A sensitivity analysis of the dynamic properties of the system, i.e. natural frequencies and mode shapes is performed considering the influence of the boundary conditions, the elastic modulus of concrete, the material properties of the asphalt layer, the expansion joints of the bridge and the interaction between the deck and the abutments of the system. Furthermore, an experimental campaign was performed during winter weather conditions and compared to a previously developed study of the same system during autumn weather conditions. The results show the great influence the weather conditions on the dynamic properties of the system as well as the limitation, uncertainties and the problem of the unicity of the solution for the calibration of the developed FE-models. The case study shows the importance of SHM not only for tracking the dynamic properties of the studied system and early detection of global changes of the system but also how performing measurements can help to reduce the inherent uncertainties associated to a FE-model to improve the current engineering practice.