In recent years, an increasing number of researchers have become involved in wireless sensor networks (WSNs) and cloud computing. However, integrating WSN and cloud computing technology to monitor the environment is still an open issue. In this paper, we propose a WSN and a mobile-device-based environmental monitor based on SaaS (Software as a Service) of cloud computing architecture. In the first scheme, we provide a spare two-tier data aggregation of WSNs which can automatically report event data (such as flood and fire events) to cloud servers. We also use a NS2 simulation tool to implement and prove that our automatic report model will outperform other schemes. The second model is a mobile-device-based event reporting scheme. In an environmental monitoring system since there are some events (such as structural damage to dams and bridges) that cannot be reported automatically, we propose using a mobile device to report such events. The proposed second scheme can defend against Denial of Service (DoS) and man-in-the-middle attacks, achieve mutual authentication, ensure data security and address network security issues.