The thermal stresses in a concrete bridge are affected by the surrounding climate. Varying temperature will produce movements which, if restrained, may induce stresses in the structure. To predict the thermal stresses due to climatic effects in concrete box cross-sections, FE simulations have been performed with extensive climatic input data to simulate the temperature and resulting stress fields in the hollow concrete arch of the New Svinesund Bridge. A linear temperature difference approach may overestimate the thermal tension stresses on the inside surface of the walls. Varying thickness between the walls will give more unfavourable stresses than identical wall thicknesses. The cross-sectional height and width together with orientation of the bridge are of less importance concerning thermal stresses.