Under the Köppen climate classification, Dhaka has a tropical savanna climate (Köppen ''Aw''). The city has a distinct monsoonal season, with an annual average temperature of  and monthly means varying between  in January and  in May. Approximately 87% of the average annual rainfall of  occurs between May and October. Increasing air and water pollution emanating from traffic congestion and industrial waste are serious problems affecting public health and the quality of life in the city. Water bodies and wetlands around Dhaka are facing destruction as these are being filled up to construct multi-storied buildings and other real estate developments. Coupled with pollution, such erosion of natural habitats threatens to destroy much of the regional biodiversity.