What is the weather like in Tanzania/Zanzibar?
There is a well established weather pattern. The monsoon normally arrives late March lasting until late May. This is not the time to visit. April is the wettest month of the year, with May not far behind, usually up to 15 inches of rain each month and, on average, up to 20 days of rain. Several hotels and many camps/lodges in the parks close at this time. You will not see Tanzania/Zanzibar at its best.
June through to October is glorious, relatively cool with temperatures in the mid 70s – 80s and relatively low humidity.
From October on it starts to warm up. Late November is called “the short rains” when there can be some extended periods of rain, but should not spoil a holiday taken at this time. In to January it starts to get hotter and more humid as the monsoon approaches. At this time of the year it is best, for a comfortable nights sleep, to stay at hotels which have air-conditioned bedrooms.