In the frame of international deployment of hydrogen infrastructure, with the overarching goal of evaluating, optimising and improving related technical regulations and standards, tests on full-scale high pressure tanks for on board hydrogen storage are ongoing at the GasTeF facility of the JRC. This facility is able to execute hydrogen cycling tests, including in-situ temperature measurements of local gas temperatures during refueling up to a maximum pressure up to 85 MPa. In this paper we present the influence of the initial tank's gas and walls' temperature on the evolution of the gas temperature during hydrogen refueling of two different types of tanks. The experiments have been assisted by 3-dimensional CFD simulations of the phenomena. The experimental data show that the maximum gas temperature reached at the end of the filling increases linearly with the ambient temperature and that the temperature increase of the gas decreases linearly with the ambient temperature. The simulations results were consistent with the experimental findings and contributed to the interpretations of the thermodynamics phenomena.