Wireless Sensor Networks (WSN) provide a powerful combination of distributed sensing, computing and wireless communication that can be useful in various applications (monitoring, health and fitness, environment, automotive, smart building, etc.). However, energy consumption is a critical issue in the deployment of battery-powered wireless sensor networks. Therefore, energy harvesting provides a potential solution to extend the system lifetime. This paper addresses the problematic of using wind as harvesting source, and weather forecast to improve the prediction of wind condition in the near future. The related issues concern the wind behavior in outdoor condition which is irregular and unpredictable. A wind harvester (a small wind turbine) is considered in order to define a model that translates a weather forecast (the wind speed) into a corresponding energy harvesting prediction. The proposed network architecture has therefore to manage the retrieval of weather forecast from Internet and transmit this information to the end devices. Moreover, the renewable energy storage device needs to be properly sized in order to provide power to the end devices when no more energy can be harvested from the ambient environment. For that, it is required to store a part of the harvested energy when it is available, and this is the role of a power manager (PM). In this paper, we propose different PM policies, two of them exploiting the use of weather forecast to improve the prediction accuracy for WSN nodes.