Weather has a significant influence on navigation processes. Driving dur-ing a heavy rain, for example, is slower and due to poor visibility more dangerous than driving in perfect weather conditions. Thus from time management and safety perspective including weather information is bene-ficial. Weather, especially rain may also be critical for transportation tasks since some commodities like straw or sand should not get wet. In the last years, the quality of weather information and weather forecast has im-proved and could be used to improve route planning. The paper discusses how weather information can be included in route planning algorithms. A first approximating algorithm to incorporate weather forecast data is pre-sented. Some examples showing the impact on route planning conclude the paper.