CLIM2POWER will develop a climate service that integrates seasonal weather forecasts into decision making in the electricity sector. In particular, we assess the value of current and possible future seasonal forecasts for an improved management of power generation portfolios. For that purpose, cutting-edge seasonal forecasts are down-scaled and coupled with stochastic power system models to estimate the impact of seasonal weather conditions on renewable electricity generation and electricity and district heating demand. Subsequently, we derive optimal operation schedules for the electricity sector, such as optimal operation of hydro-storage and of fossil fuel acquisition, applying a set of existing bottom-up, technology rich power system models. Possible impacts from changing renewable supply and demand on the power-system as a whole and electricity prices are also derived. While the final climate service is going to be made available for the whole Europe, we additionally develop four regional case studies in Portugal, France, Sweden and in the German-Austrian market zone to validate the European model. Additionally, the case studies put a different focus on markets and market prices, dam operation restrictions due to ecological regulation in the river systems, and flexibility options in the power sector. As climate change may introduce changes to the seasonality of climate processes, future climate scenarios are assessed in an additional sensitivity analysis. The climate service is developed together with important stakeholders from the sector in an iterative process and is made available as public web service online. In particular power generation & trading companies, power system operators & regulators, power consumers, and water managers are going to directly profit from the outcome of our project.