The Lake Manyara basin has an altitudinal range of around 950 - 1500m, which means that while it receives an average of 650mm of rainfall, the climatic picture is slightly more complicated than one might think, ranging from arid (Masai Plains) to semi-arid (Ardan Plains) to humid (highlands). The park itself is equally varied, with the north twice as dry as the south. The lake lies at 945m, is flanked to the west by the Rift Valley’s escarpment and receives an average of 750mm a year, a semi-arid to humid yield supplemented by both ground and surface water sources. The upshot is an area rich in flora - groundwater forest, acacia woodland, mixed woodland, grasslands and swamp - and therefore in fauna, with especially dense populations of elephant and buffalo providing evidence of the area’s relative wetness. The average temperature for the park is 22°C
So, in terms of visiting Lake Manyara National Park, March - May is great for bird watching, while June through to October and January and February (when it is dry and the animals are forced to utilise fewer standing water sources) is fantastic for game viewing.*
*This said, recent research shows that the park is naturally susceptible to swinging between extreme low and extreme high rainfall periods, a long term cycle that will obviously affect the movement of the area’s wildlife.