During the last decade, cloud computing became a natural choice to host and provide various computing resources as on-demand services. The correct characterization and management of cloud environment objects (clouds, data centers, providers, services, data, users, etc.) is the first step towards effective provisioning and integration of cloud services. However, cloud computing environment is often subject to uncertainty. This could be attributed to the incompleteness and imprecision of cloud available information, as well as the highly changing conditions. The purpose of this survey is to study, criticize and classify the already existing works that deal with uncertainty in the cloud. We present a taxonomy on the uncertainty in the cloud and we study how such concept was tackled by researchers in cloud environments. Finally, we identify the challenges and the requirements to deal with uncertain data in the cloud, as well as the future directions.